public int getClientPort() {
    return activeZKServerIndex < 0 || activeZKServerIndex >= clientPortList.size()
      ? -1
      : clientPortList.get(activeZKServerIndex);
  }
Kill one back up ZK servers.
@throws IOException if waiting for the shutdown of a server fails
hbase-zookeeper/src/main/java/org/apache/hadoop/hbase/zookeeper/MiniZooKeeperCluster.java