YARN-1639. Modified RM HA configuration handling to have a way of not requiring separate configuration files for each RM. Contributed by Xuan Gong.
svn merge --ignore-ancestry -c 1564032 ../../trunk/


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1564033 13f79535-47bb-0310-9956-ffa450edef68