default void preRenameRSGroup(final ObserverContext<MasterCoprocessorEnvironment> ctx,
    final String oldName, final String newName) throws IOException {
  }
Called before rename rsgroup.
@param ctx     the environment to interact with the framework and master
@param oldName old rsgroup name
@param newName new rsgroup name
hbase-server/src/main/java/org/apache/hadoop/hbase/coprocessor/MasterObserver.java