Added management instance handler and some refactoring

- Added management instance handler to provide management network
  connectivity for the management network connected instance, currenly
  local managemenet network connectivity provided
- Renamed Dummy service to Default service
- Renamed CordVtnInstanceHandler to AbstractInstanceHandler and moved
  default VTN rule populations to DefaultInstanceHandler
- Removed workaround management network access code from OLT agent
  instance handler

Change-Id: I990c29b8ae41674d136fbc12f3c4e92167c8c74c
diff --git a/src/main/java/org/opencord/cordvtn/api/Instance.java b/src/main/java/org/opencord/cordvtn/api/Instance.java
index 3945a9d..23841b6 100644
--- a/src/main/java/org/opencord/cordvtn/api/Instance.java
+++ b/src/main/java/org/opencord/cordvtn/api/Instance.java
@@ -22,7 +22,7 @@
 import org.onosproject.net.Host;
 import org.onosproject.net.PortNumber;
 import org.onosproject.xosclient.api.VtnPortId;
-import org.onosproject.xosclient.api.VtnService;
+import org.onosproject.xosclient.api.VtnServiceApi.ServiceType;
 import org.onosproject.xosclient.api.VtnServiceId;
 
 import static com.google.common.base.Preconditions.checkArgument;
@@ -91,9 +91,9 @@
      *
      * @return vtn service type
      */
-    public VtnService.ServiceType serviceType() {
+    public ServiceType serviceType() {
         String serviceType = host.annotations().value(SERVICE_TYPE);
-        return VtnService.ServiceType.valueOf(serviceType);
+        return ServiceType.valueOf(serviceType);
     }
 
     /**