Merge pick up, tweaked role/site/plcore_base or os_manager path when OpenStack not present
diff --git a/planetstack/core/models/subnet.py b/planetstack/core/models/subnet.py
index cad9fea..37175ec 100644
--- a/planetstack/core/models/subnet.py
+++ b/planetstack/core/models/subnet.py
@@ -3,6 +3,7 @@
 from django.db import models
 from core.models import PlCoreBase
 from core.models import Slice
+from openstack.manager import OpenStackManager
 
 # Create your models here.
 
@@ -17,9 +18,13 @@
     def __unicode__(self):  return u'%s' % (self.slice.name)
 
     def save(self, *args, **kwds):
-        self.os_manager.save_subnet(self)
+        if not hasattr(self, 'os_manager'):
+            setattr(self, 'os_manager', OpenStackManager())
+            self.os_manager.save_subnet(self)
         super(Subnet, self).save(*args, **kwds)
 
     def delete(self, *args, **kwds):
-        self.os_manager.delete_subnet(self)
+        if not hasattr(self, 'os_manager'):
+            setattr(self, 'os_manager', OpenStackManager())
+            self.os_manager.delete_subnet(self)
         super(Subnet, self).delete(*args, **kwds)