log timestamping error on Link remove

Change-Id: Ia333fb4f9c4af3642482f626e5660e0339d13995
diff --git a/core/store/dist/src/main/java/org/onlab/onos/store/link/impl/GossipLinkStore.java b/core/store/dist/src/main/java/org/onlab/onos/store/link/impl/GossipLinkStore.java
index ab5cc8a..29669af 100644
--- a/core/store/dist/src/main/java/org/onlab/onos/store/link/impl/GossipLinkStore.java
+++ b/core/store/dist/src/main/java/org/onlab/onos/store/link/impl/GossipLinkStore.java
@@ -377,6 +377,7 @@
         try {
             timestamp = deviceClockService.getTimestamp(dstDeviceId);
         } catch (IllegalStateException e) {
+            log.warn("Failed to remove link {}, was not the master", key);
             //there are times when this is called before mastership
             // handoff correctly completes.
             return null;