fix: (vNet) class load issues for OSGi bundle.

Problem.
1. Inside incubator package, class loader can't search classes defined
   in the other bundles such as onos-core

Solution
1. Added a method to return bundle context, and obtain class loader.

Change-Id: If5ee4cb1a5b9ef5ab7d7e3bbc70408ea8257baea
diff --git a/incubator/net/src/main/java/org/onosproject/incubator/net/virtual/impl/VirtualNetworkLinkManager.java b/incubator/net/src/main/java/org/onosproject/incubator/net/virtual/impl/VirtualNetworkLinkManager.java
index 3a93e3c..ed18f86 100644
--- a/incubator/net/src/main/java/org/onosproject/incubator/net/virtual/impl/VirtualNetworkLinkManager.java
+++ b/incubator/net/src/main/java/org/onosproject/incubator/net/virtual/impl/VirtualNetworkLinkManager.java
@@ -51,7 +51,7 @@
      */
     public VirtualNetworkLinkManager(VirtualNetworkService virtualNetworkManager,
                                      NetworkId networkId) {
-        super(virtualNetworkManager, networkId);
+        super(virtualNetworkManager, networkId, LinkEvent.class);
     }
 
     @Override