YARN-1734. Fixed ResourceManager to update the configurations when it transits from standby to active mode so as to assimilate any changes that happened while it was in standby mode. Contributed by Xuan Gong.
svn merge --ignore-ancestry -c 1571539 ../../trunk/


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2.4@1571541 13f79535-47bb-0310-9956-ffa450edef68