Fix type mismatch

Change-Id: I26d094c4ae0d7c6699e49a0aa9885bd4d6d89e33
diff --git a/utils/netty/src/main/java/org/onlab/netty/NettyMessagingService.java b/utils/netty/src/main/java/org/onlab/netty/NettyMessagingService.java
index b84e193..661e288 100644
--- a/utils/netty/src/main/java/org/onlab/netty/NettyMessagingService.java
+++ b/utils/netty/src/main/java/org/onlab/netty/NettyMessagingService.java
@@ -231,7 +231,7 @@
 
     @Override
     public void unregisterHandler(String type) {
-        handlers.remove(type);
+        handlers.remove(hashToLong(type));
     }
 
     private MessageHandler getMessageHandler(long type) {