register DefaultGroupId to Kryo

Change-Id: I650482164acf4b97f1bcd1a1633806a3b526a14d
diff --git a/core/store/serializers/src/main/java/org/onlab/onos/store/serializers/KryoNamespaces.java b/core/store/serializers/src/main/java/org/onlab/onos/store/serializers/KryoNamespaces.java
index 5e0c6dd..e29423c 100644
--- a/core/store/serializers/src/main/java/org/onlab/onos/store/serializers/KryoNamespaces.java
+++ b/core/store/serializers/src/main/java/org/onlab/onos/store/serializers/KryoNamespaces.java
@@ -31,6 +31,7 @@
 import org.onlab.onos.cluster.NodeId;
 import org.onlab.onos.cluster.RoleInfo;
 import org.onlab.onos.core.DefaultApplicationId;
+import org.onlab.onos.core.DefaultGroupId;
 import org.onlab.onos.mastership.MastershipTerm;
 import org.onlab.onos.net.ConnectPoint;
 import org.onlab.onos.net.DefaultAnnotations;
@@ -298,6 +299,7 @@
             .register(ReadStatus.class)
             .register(WriteStatus.class)
             .register(VersionedValue.class)
+            .register(DefaultGroupId.class)
 
             .build();