STORM-3986 - Get rid of BlacklistScheduler timer [INFO] logs

Author: rzo1

storm-server/src/main/java/org/apache/storm/scheduler/blacklist/BlacklistScheduler.java

@@ -194,7 +194,11 @@ private Set<String> refreshBlacklistedSupervisorIds(Cluster cluster, Topologies
                 new ArrayList<>(badSupervisorsToleranceSlidingWindow),
                 new ArrayList<>(sendAssignmentFailureCount),
                 cluster, topologies);
-        LOG.info("Supervisors {} are blacklisted.", blacklistedSupervisors);
+        if (blacklistedSupervisors.isEmpty()) {
+            LOG.debug("No Supervisors are blacklisted.");
+        } else {
+            LOG.info("Supervisors {} are blacklisted.", blacklistedSupervisors);
+        }
         return blacklistedSupervisors;
     }