SLING-5280 : change the separate self-check of the HeartbeatHandler to call checkForLocalClusterViewChange only - instead of checkForTopologyChange - reason being that the former does not call into the AnnouncementRegistry which could be blocked in the very same case this self-check should help
sling/trunk/bundles/extensions/discovery/impl/src/main/java/org/apache/sling/discovery/impl/DiscoveryServiceImpl.java