create OSModelAdmin. Update some Admin definitions to subclass OSModelAdmin
diff --git a/plstackapi/core/models/role.py b/plstackapi/core/models/role.py
index 4b4b2e4..b9f3e2f 100644
--- a/plstackapi/core/models/role.py
+++ b/plstackapi/core/models/role.py
@@ -2,9 +2,6 @@
 import datetime
 from django.db import models
 from plstackapi.core.models import PlCoreBase
-from plstackapi.openstack.driver import OpenStackDriver
-
-# Create your models here.
 
 class Role(PlCoreBase):
 
@@ -16,17 +13,13 @@
 
 
     def save(self, *args, **kwds):
-        driver = OpenStackDriver() 
         if not self.role_id:
-            keystone_role = driver.create_role(name=self.role_type)
+            keystone_role = self.driver.create_role(name=self.role_type)
             self.role_id = keystone_role.id
-
         super(Role, self).save(*args, **kwds)
     
     def delete(self, *args, **kwds):
-        driver = OpenStackDriver()
         if self.role_id:
-            driver.delete_role({'id': self.role_id})   
-
+            self.driver.delete_role({'id': self.role_id})   
         super(Role, self).delete(*args, **kwds)
             
diff --git a/plstackapi/core/models/site.py b/plstackapi/core/models/site.py
index 1e1cbe4..67b3e52 100644
--- a/plstackapi/core/models/site.py
+++ b/plstackapi/core/models/site.py
@@ -2,9 +2,6 @@
 from django.db import models
 from plstackapi.core.models import PlCoreBase
 from plstackapi.core.models import DeploymentNetwork
-from plstackapi.openstack.driver import OpenStackDriver
-
-# Create your models here.
 
 
 class Site(PlCoreBase):
@@ -24,26 +21,24 @@
     def __unicode__(self):  return u'%s' % (self.name)
 
     def save(self, *args, **kwds):
-        driver  = OpenStackDriver()
         if not self.tenant_id:
-            tenant = driver.create_tenant(tenant_name=self.login_base, 
-                                          description=self.name, 
-                                          enabled=self.enabled)
+            tenant = self.driver.create_tenant(tenant_name=self.login_base, 
+                                               description=self.name, 
+                                               enabled=self.enabled)
             self.tenant_id = tenant.id
         # update the record
         if self.id:
-            driver.update_tenant(self.tenant_id, 
-                                 name=self.login_base,
-                                 description=self.name,
-                                 enabled=self.enabled)
+            self.driver.update_tenant(self.tenant_id, 
+                                      name=self.login_base,
+                                      description=self.name,
+                                      enabled=self.enabled)
 
         super(Site, self).save(*args, **kwds)               
 
 
     def delete(self, *args, **kwds):
-        driver = OpenStackDriver()
         if self.tenant_id:
-            driver.delete_tenant(self.tenant_id)
+            self.driver.delete_tenant(self.tenant_id)
         super(Site, self).delete(*args, **kwds)         
         
 
diff --git a/plstackapi/core/models/slice.py b/plstackapi/core/models/slice.py
index 27184dc..d174b2e 100644
--- a/plstackapi/core/models/slice.py
+++ b/plstackapi/core/models/slice.py
@@ -5,7 +5,6 @@
 from plstackapi.core.models import PLUser
 from plstackapi.core.models import Role
 from plstackapi.core.models import DeploymentNetwork
-from plstackapi.openstack.driver import OpenStackDriver
 
 # Create your models here.
 
@@ -25,31 +24,28 @@
     def __unicode__(self):  return u'%s' % (self.name)
 
     def save(self, *args, **kwds):
-
-        driver = OpenStackDriver()
         if not self.tenant_id:
             nova_fields = {'tenant_name': self.name,
                    'description': self.description,
                    'enabled': self.enabled}
-            tenant = driver.create_tenant(**nova_fields)
+            tenant = self.driver.create_tenant(**nova_fields)
             self.tenant_id = tenant.id
 
             # create network
-            network = driver.create_network(self.name)
+            network = self.driver.create_network(self.name)
             self.network_id = network['id']
 
             # create router
-            router = driver.create_router(self.name)
+            router = self.driver.create_router(self.name)
             self.router_id = router['id']
 
         super(Slice, self).save(*args, **kwds)
 
     def delete(self, *args, **kwds):
-        driver = OpenStackDriver()
         if self.tenant_id:
-            driver.delete_router(self.router_id)
-            driver.delete_network(self.network_id)
-            driver.delete_tenant(self.tenant_id)
+            self.driver.delete_router(self.router_id)
+            self.driver.delete_network(self.network_id)
+            self.driver.delete_tenant(self.tenant_id)
 
         super(Slice, self).delete(*args, **kwds)    
 
diff --git a/plstackapi/core/models/sliver.py b/plstackapi/core/models/sliver.py
index 27b9ab1..13f94b2 100644
--- a/plstackapi/core/models/sliver.py
+++ b/plstackapi/core/models/sliver.py
@@ -9,7 +9,6 @@
 from plstackapi.core.models import Node
 from plstackapi.core.models import Site
 from plstackapi.core.models import DeploymentNetwork
-from plstackapi.openstack.driver import OpenStackDriver
 
 # Create your models here.
 class Sliver(PlCoreBase):
@@ -30,8 +29,7 @@
             raise exceptions.ValidationError, "Slice %s has no subnet" % self.slice.name
 
         if not self.instance_id:
-            driver = OpenStackDriver()
-            instance = driver.spawn_instance(name=self.name,
+            instance = self.driver.spawn_instance(name=self.name,
                                    key_name = self.key.name,
                                    flavor_id = self.flavor.flavor_id,
                                    image_id = self.image.image_id,
@@ -41,8 +39,7 @@
         super(Sliver, self).save(*args, **kwds)
 
     def delete(self, *args, **kwds):
-        driver = OpenStackDriver()
         if self.instance_id:
-            driver.destroy_instance(self.instance_id)
+            self.driver.destroy_instance(self.instance_id)
 
         super(Sliver, self).delete(*args, **kwds)
diff --git a/plstackapi/core/models/subnet.py b/plstackapi/core/models/subnet.py
index 2e10ae1..c9ea1ef 100644
--- a/plstackapi/core/models/subnet.py
+++ b/plstackapi/core/models/subnet.py
@@ -3,7 +3,6 @@
 from django.db import models
 from plstackapi.core.models import PlCoreBase
 from plstackapi.core.models import Slice
-from plstackapi.openstack.driver import OpenStackDriver
 
 # Create your models here.
 
@@ -18,10 +17,8 @@
     def __unicode__(self):  return u'%s' % (self.slice.name)
 
     def save(self, *args, **kwds):
-
-        driver = OpenStackDriver()
         if not self.subnet_id:
-            quantum_subnet = driver.create_subnet(name= self.slice.name,
+            quantum_subnet = self.driver.create_subnet(name= self.slice.name,
                                           network_id=self.slice.network_id,
                                           cidr_ip = self.cidr,
                                           ip_version=self.ip_version,
@@ -29,17 +26,16 @@
                                           end = self.end)
             self.subnet_id = quantum_subnet['id']
             # add subnet as interface to slice's router
-            driver.add_router_interface(self.slice.router_id, self.subnet_id)
+            self.driver.add_router_interface(self.slice.router_id, self.subnet_id)
             #add_route = 'route add -net %s dev br-ex gw 10.100.0.5' % self.cidr
             #commands.getstatusoutput(add_route)
 
         super(Subnet, self).save(*args, **kwds)
 
     def delete(self, *args, **kwds):
-        driver = OpenStackDriver()
         if self.subnet_id:
-            driver.delete_router_interface(self.slice.router_id, self.subnet_id) 
-            driver.delete_subnet(self.subnet_id)
+            self.driver.delete_router_interface(self.slice.router_id, self.subnet_id) 
+            self.driver.delete_subnet(self.subnet_id)
             #del_route = 'route del -net %s' % self.cidr 
             #commands.getstatusoutput(del_route)
         super(Subnet, self).delete(*args, **kwds)