@Override
  public void nodeChildrenChanged(String path) {
    if (path.equals(watcher.getZNodePaths().backupMasterAddressesZNode)) {
      loadBackupMasters();
    }
  }
Construct a master address listener with the specified <code>zookeeper</code> reference.
<p>
This constructor does not trigger any actions, you must call methods explicitly. Normally you
will just want to execute {@link #start()} to begin tracking of the master address.
@param watcher   zk reference and watcher
@param abortable abortable in case of fatal error
hbase-zookeeper/src/main/java/org/apache/hadoop/hbase/zookeeper/MasterAddressTracker.java