[hms] Reduce noisy logging on non-leader masters.

Recently while reviewing kudu master logs in a cluster with HMS sync
enabled I noticed many occurances of the below log on the follower
masters:

   I0323 20:38:12.824517  6245 hms_notification_log_listener.cc:227] Skipping Hive Metastore notification log poll: Illegal state: Not the leader. …

I lowered the log level so it would not be logged in the common case
given this is frequent, expected, and ignored.

Change-Id: I0fa308727a71f51ded780eb97d9cdc87cb6f9069
Reviewed-on: http://gerrit.cloudera.org:8080/16203
Reviewed-by: Andrew Wong <[email protected]>
Tested-by: Kudu Jenkins
Reviewed-by: Attila Bukor <[email protected]>

src/kudu/master/hms_notification_log_listener.cc

@@ -227,7 +227,7 @@ Status HmsNotificationLogListenerTask::Poll() {
   // This method calls the catalog manager directly, so ensure the leader lock is held.
   CatalogManager::ScopedLeaderSharedLock l(catalog_manager_);
   if (!l.first_failed_status().ok()) {
-    LOG(INFO) << "Skipping Hive Metastore notification log poll: "
+    VLOG(1) << "Skipping Hive Metastore notification log poll: "
               << l.first_failed_status().ToString();
     return Status::OK();
   }