public void start() throws IOException {
    if (zooKeeperClient != null) {
      String principal = ZookeeperUtils.setupZookeeperAuth(
          conf, saslLoginContextName, zkPrincipal, zkKeytab);
      if (principal != null) {
        userNameFromPrincipal = LlapUtil.getUserNameFromPrincipal(principal);
      }
      zooKeeperClient.start();
    }
    // Init closeable utils in case register is not called (see HIVE-13322)
    CloseableUtils.class.getName();
  }
Get the ensemble server addresses from the configuration. The format is: host1:port,
host2:port..

@param conf configuration
llap-client/src/java/org/apache/hadoop/hive/registry/impl/ZkRegistryBase.java