Kryo related fixes

- KryoNamespace to allow control over registration id

Change-Id: Idc2a0e27a09916657c725ee97e4366109144cc66
diff --git a/utils/netty/src/main/java/org/onlab/netty/InternalMessage.java b/utils/netty/src/main/java/org/onlab/netty/InternalMessage.java
index a981c34..40b529e 100644
--- a/utils/netty/src/main/java/org/onlab/netty/InternalMessage.java
+++ b/utils/netty/src/main/java/org/onlab/netty/InternalMessage.java
@@ -34,6 +34,13 @@
     // Must be created using the Builder.
     private InternalMessage() {}
 
+    InternalMessage(long id, Endpoint sender, String type, byte[] payload) {
+        this.id = id;
+        this.sender = sender;
+        this.type = type;
+        this.payload = payload;
+    }
+
     public long id() {
         return id;
     }