ONOS-2725: Fix subscriber registration for link inject request

Change-Id: I56a651a561a4fe59161ad00dbd28e28fad6731c9

@@ -148,6 +148,7 @@ public class ECLinkStore
         clusterCommunicator.addSubscriber(LINK_INJECT_MESSAGE,
         clusterCommunicator.addSubscriber(LINK_INJECT_MESSAGE,
                 SERIALIZER::decode,
                 SERIALIZER::decode,
                 this::injectLink,
                 this::injectLink,
+                SERIALIZER::encode,
                 SharedExecutors.getPoolThreadExecutor());
                 SharedExecutors.getPoolThreadExecutor());
 
 
         linkDescriptions.addListener(linkTracker);
         linkDescriptions.addListener(linkTracker);