Bug fix for refactored DestinationSet.

The issue was in the serialization. Since we enhanced DestinationSet
to use an Enumeration class, this class should also be registered
with KryoNamespace. Without registering the Enum class
DestinationSetType, the next hops were remaining local to the instance
which has inserted them into the Map and they did not propagate to
other instances.

Change-Id: I4e21481a5fe232892319232b8675cb083593f8f1
diff --git a/app/src/main/java/org/onosproject/segmentrouting/SegmentRoutingManager.java b/app/src/main/java/org/onosproject/segmentrouting/SegmentRoutingManager.java
index 33c71f5..317e7f4 100644
--- a/app/src/main/java/org/onosproject/segmentrouting/SegmentRoutingManager.java
+++ b/app/src/main/java/org/onosproject/segmentrouting/SegmentRoutingManager.java
@@ -514,6 +514,7 @@
                 .register(DestinationSetNextObjectiveStoreKey.class,
                           VlanNextObjectiveStoreKey.class,
                           DestinationSet.class,
+                          DestinationSet.DestinationSetType.class,
                           NextNeighbors.class,
                           Tunnel.class,
                           DefaultTunnel.class,