YARN-1410. Added tests to validate that clients can fail-over to a new RM
after getting an application-ID but before submission and can still submit
to the newly active RM with no issues. Contributed by Xuan Gong.
svn merge --ignore-ancestry -c 1575478 ../../trunk/


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1575479 13f79535-47bb-0310-9956-ffa450edef68