Use LinkTuple as identifier.

- Use LinkTuple as Identifier for
  - Link, LinkEvent
- Register LinkTuple to KryoFactory
- Fix mocked Link to return LinkTuple

Change-Id: Ie58f31d4b2c906bc2343e2414d06190828e7e5c9
diff --git a/src/main/java/net/onrc/onos/core/topology/LinkImpl.java b/src/main/java/net/onrc/onos/core/topology/LinkImpl.java
index 26c260a..a573540 100644
--- a/src/main/java/net/onrc/onos/core/topology/LinkImpl.java
+++ b/src/main/java/net/onrc/onos/core/topology/LinkImpl.java
@@ -2,6 +2,8 @@
 
 import java.util.Map;
 
+import net.onrc.onos.core.util.LinkTuple;
+
 import org.apache.commons.lang.Validate;
 
 /**
@@ -62,6 +64,11 @@
     }
 
     @Override
+    public LinkTuple getLinkTuple() {
+        return linkObj.getLinkTuple();
+    }
+
+    @Override
     public Switch getSrcSwitch() {
         topology.acquireReadLock();
         try {