@Override
  public DataNodeConfigSource getDataNodeConfigSource(ClusterMapConfig clusterMapConfig, String zkAddr,
      DataNodeConfigSourceMetrics metrics) {
    if (dataNodeConfigSource != null) {
      return dataNodeConfigSource;
    }
    return super.getDataNodeConfigSource(clusterMapConfig, zkAddr, metrics);
  }
Return the {@link MockHelixManager}
@param clusterName unused.
@param instanceName unused.
@param instanceType unused.
@param zkAddr unused.
@return the {@link MockHelixManager}
ambry-clustermap/src/test/java/com/github/ambry/clustermap/MockHelixManagerFactory.java