default void preUpdateRSGroupConfig(final ObserverContext<MasterCoprocessorEnvironment> ctx,
    final String groupName, final Map<String, String> configuration) throws IOException {
  }
Called before update rsgroup config.
@param ctx           the environment to interact with the framework and master
@param groupName     the group name
@param configuration new configuration of the group name to be set
hbase-server/src/main/java/org/apache/hadoop/hbase/coprocessor/MasterObserver.java