public HashMap<String, byte[]> waitForCompletedWithRet()
    throws ForeignException, InterruptedException {
    waitForCompleted();
    return dataFromFinishedMembers;
  }
Waits until the entire procedure has globally completed, or has been aborted. If an exception
is thrown the procedure may or not have run cleanup to trigger the completion latch yet.
@return data returned from procedure members upon successfully completing subprocedure.
hbase-server/src/main/java/org/apache/hadoop/hbase/procedure/Procedure.java