default BalanceResponse balanceRSGroup(String groupName) throws IOException {
    return balanceRSGroup(groupName, BalanceRequest.defaultInstance());
  }
Balance regions in the given RegionServer group
@param groupName the group name
@return BalanceResponse details about the balancer run
@throws IOException if a remote or network exception occurs
hbase-client/src/main/java/org/apache/hadoop/hbase/client/Admin.java