Fix Mastership timstamping issue

Change-Id: I80cfa71f844ddf7d64dbff0458db193734a3f737
diff --git a/core/store/dist/src/main/java/org/onlab/onos/store/device/impl/GossipDeviceStore.java b/core/store/dist/src/main/java/org/onlab/onos/store/device/impl/GossipDeviceStore.java
index 2f1e504..31df710 100644
--- a/core/store/dist/src/main/java/org/onlab/onos/store/device/impl/GossipDeviceStore.java
+++ b/core/store/dist/src/main/java/org/onlab/onos/store/device/impl/GossipDeviceStore.java
@@ -113,6 +113,7 @@
     protected ClusterService clusterService;
 
     private static final KryoSerializer SERIALIZER = new KryoSerializer() {
+        @Override
         protected void setupKryoPool() {
             serializerPool = KryoPool.newBuilder()
                     .register(KryoPoolUtil.API)