Merge -r 1433525:1433526 from trunk to branch-2. Fixes: YARN-336. Fair scheduler FIFO scheduling within a queue only allows 1 app at a time. Contributed by Sandy Ryza.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1433549 13f79535-47bb-0310-9956-ffa450edef68