Election scheduler log (elastic#136611)

Adds a debug log to `Coordinator.startElectionScheduler()` in the case
a local node is not the master and hence cannot trigger an election
scheduler

Author: joshua-adams-1

server/src/main/java/org/elasticsearch/cluster/coordination/Coordinator.java

@@ -1812,7 +1812,7 @@ protected void onFoundPeersUpdated() {
 
                     if (foundQuorum) {
                         if (electionScheduler == null) {
-                            logger.debug("starting election scheduler, expecting votes [{}]", expectedVotes);
+                            logger.debug("preparing election scheduler, expecting votes [{}]", expectedVotes);
                             startElectionScheduler();
                         }
                     } else {
@@ -1834,8 +1834,10 @@ private void startElectionScheduler() {
         assert electionScheduler == null : electionScheduler;
 
         if (getLocalNode().isMasterNode() == false) {
+            logger.debug("local node is not the master, skipping election scheduler");
             return;
         }
+        logger.debug("starting election scheduler");
 
         final TimeValue gracePeriod = TimeValue.ZERO;
         electionScheduler = electionSchedulerFactory.startElectionScheduler(gracePeriod, new Runnable() {