private void update(String path) {
    if (path.startsWith(watcher.getZNodePaths().masterMaintZNode)) {
      update();
    }
  }
Tracks the master Maintenance Mode via ZK. Unused. Used to be set by hbck to prevent concurrent
splits/merges, but those use PV2 now and HBCK2 uses it's own service, so no longer an issue. Left
in, in case we need to use this for the incomplete parts of HBCK2...
hbase-zookeeper/src/main/java/org/apache/hadoop/hbase/zookeeper/MasterMaintenanceModeTracker.java