List<InstanceConfig> getInstanceConfigsFromDcs(String[] dcNames) {
    List<InstanceConfig> configs = new ArrayList<>();
    for (String dcName : dcNames) {
      MockHelixAdmin helixAdmin = helixAdmins.get(dataCenterToZkAddress.get(dcName).getZkConnectStrs().get(0));
      configs.addAll(helixAdmin.getInstanceConfigs(clusterName));
    }
    return configs;
  }
Get instance configs from specified datacenters.
@param dcNames array of dc names
@return a list of InstanceConfigs that from required datacenters.
ambry-clustermap/src/test/java/com/github/ambry/clustermap/MockHelixCluster.java