Lower log level for warning message seen when starting larger clusters

Also fix message to show id instead of null

Change-Id: I91b131674088d644ee10f5d105052c42cc018984
diff --git a/core/store/dist/src/main/java/org/onosproject/store/cluster/impl/DistributedClusterStore.java b/core/store/dist/src/main/java/org/onosproject/store/cluster/impl/DistributedClusterStore.java
index 78110c83e..5e4e71c 100644
--- a/core/store/dist/src/main/java/org/onosproject/store/cluster/impl/DistributedClusterStore.java
+++ b/core/store/dist/src/main/java/org/onosproject/store/cluster/impl/DistributedClusterStore.java
@@ -256,7 +256,7 @@
             ControllerNode node = allNodes.get(nodeId);
             // Either this node or that node is no longer part of the same cluster
             if (node == null) {
-                log.warn("Could not find node {} in the cluster, ignoring state change", node);
+                log.debug("Could not find node {} in the cluster, ignoring state change", nodeId);
                 return;
             }
             ClusterEvent.Type type = newState == State.READY ? INSTANCE_READY :