Fixed a defect in topology view handler where listeners were being removed prematurely.

Change-Id: I48e2a719be726e557ecf57759799ae63e4ac122f
diff --git a/web/gui/src/main/java/org/onosproject/ui/impl/TopologyViewMessageHandler.java b/web/gui/src/main/java/org/onosproject/ui/impl/TopologyViewMessageHandler.java
index 3be244e..854ac5a 100644
--- a/web/gui/src/main/java/org/onosproject/ui/impl/TopologyViewMessageHandler.java
+++ b/web/gui/src/main/java/org/onosproject/ui/impl/TopologyViewMessageHandler.java
@@ -162,6 +162,7 @@
     @Override
     public void destroy() {
         cancelAllRequests();
+        removeListeners();
         super.destroy();
     }
 
@@ -245,7 +246,6 @@
     private void cancelAllRequests() {
         stopSummaryMonitoring();
         stopTrafficMonitoring();
-        removeListeners();
     }
 
     // Sends all controller nodes to the client as node-added messages.