Changed netty message type to String from Long to avoid potential collisions

Change-Id: I42014a920917a8022744ae15a9fefa6bae6890a7
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 f9d4e0b..ba3c896 100644
--- a/utils/netty/src/main/java/org/onlab/netty/InternalMessage.java
+++ b/utils/netty/src/main/java/org/onlab/netty/InternalMessage.java
@@ -27,19 +27,18 @@
  */
 public final class InternalMessage implements Message {
 
-    public static final long REPLY_MESSAGE_TYPE =
-            NettyMessagingService.hashToLong("NETTY_MESSAGING_REQUEST_REPLY");
+    public static final String REPLY_MESSAGE_TYPE = "NETTY_MESSAGING_REQUEST_REPLY";
 
     private long id;
     private Endpoint sender;
-    private long type;
+    private String type;
     private byte[] payload;
     private transient NettyMessagingService messagingService;
 
     // Must be created using the Builder.
     private InternalMessage() {}
 
-    InternalMessage(long id, Endpoint sender, long type, byte[] payload) {
+    InternalMessage(long id, Endpoint sender, String type, byte[] payload) {
         this.id = id;
         this.sender = sender;
         this.type = type;
@@ -50,7 +49,7 @@
         return id;
     }
 
-    public long type() {
+    public String type() {
         return type;
     }
 
@@ -104,7 +103,7 @@
             return this;
         }
 
-        public Builder withType(long type) {
+        public Builder withType(String type) {
             message.type = type;
             return this;
         }