@Override
  public String getPort() {
    return String.valueOf(dataNodeWrapperList.get(0).getPort());
  }
Get connection to ConfigNode-Leader in ClusterIT environment

<p>Notice: The caller should always use try-with-resource to invoke this interface in order to
return client to ClientPool automatically

@return {@link SyncConfigNodeIServiceClient} that connects to the ConfigNode-Leader
integration-test/src/main/java/org/apache/iotdb/it/env/cluster/env/AbstractEnv.java