Network Graph Refactoring: create a separate NetworkGraphImpl instance
within TopologyManager instead of extending it.

Change-Id: I01126a2004af984b873e46d86fbe521ca1f86ddb
diff --git a/src/test/java/net/onrc/onos/intent/MockNetworkGraph.java b/src/test/java/net/onrc/onos/intent/MockNetworkGraph.java
index cde98f0..ce857de 100644
--- a/src/test/java/net/onrc/onos/intent/MockNetworkGraph.java
+++ b/src/test/java/net/onrc/onos/intent/MockNetworkGraph.java
@@ -9,7 +9,7 @@
 public class MockNetworkGraph extends NetworkGraphImpl {
 	public Switch addSwitch(Long switchId) {
 		SwitchImpl sw = new SwitchImpl(this, switchId);
-		switches.put(sw.getDpid(), sw);
+		this.putSwitch(sw);
 		return sw;
 
 	}