svn merge -c 1507135 FIXES: MAPREDUCE-5386. Ability to refresh history server job retention and job cleaner settings. Contributed by Ashwin Shankar


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1507378 13f79535-47bb-0310-9956-ffa450edef68