Adding some tests for GossipDeviceStore + bugfix

Change-Id: Ic0d55fa499b1d66131f059b4a47cd105c55a6e63
diff --git a/core/store/serializers/src/main/java/org/onlab/onos/store/serializers/KryoPoolUtil.java b/core/store/serializers/src/main/java/org/onlab/onos/store/serializers/KryoPoolUtil.java
index efecb6c..f81a984 100644
--- a/core/store/serializers/src/main/java/org/onlab/onos/store/serializers/KryoPoolUtil.java
+++ b/core/store/serializers/src/main/java/org/onlab/onos/store/serializers/KryoPoolUtil.java
@@ -31,6 +31,9 @@
 import org.onlab.packet.IpPrefix;
 import org.onlab.util.KryoPool;
 
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.ImmutableMap;
+
 public final class KryoPoolUtil {
 
     /**
@@ -47,12 +50,15 @@
      */
     public static final KryoPool API = KryoPool.newBuilder()
             .register(MISC)
+            .register(ImmutableMap.class, new ImmutableMapSerializer())
+            .register(ImmutableList.class, new ImmutableListSerializer())
             .register(
                     //
                     ArrayList.class,
                     Arrays.asList().getClass(),
                     HashMap.class,
                     //
+                    //
                     ControllerNode.State.class,
                     Device.Type.class,
                     DefaultAnnotations.class,