MulticastRouteManager: remove sink on deactivate

Reactivating this app after deactivating it once blows up on the
logs because the sink had not been properly removed - we can't
add it in that case.

Change-Id: I7c4a40f0d5b28d8c0b0d6e17737b958a65ccfd5b
diff --git a/incubator/net/src/main/java/org/onosproject/incubator/net/mcast/impl/MulticastRouteManager.java b/incubator/net/src/main/java/org/onosproject/incubator/net/mcast/impl/MulticastRouteManager.java
index ac30dda..bbc8bdb 100644
--- a/incubator/net/src/main/java/org/onosproject/incubator/net/mcast/impl/MulticastRouteManager.java
+++ b/incubator/net/src/main/java/org/onosproject/incubator/net/mcast/impl/MulticastRouteManager.java
@@ -63,6 +63,7 @@
 
     @Deactivate
     public void deactivate() {
+        eventDispatcher.removeSink(McastEvent.class);
         log.info("Stopped");
     }