HADOOP-8943. Merging change r1605857 from trunk

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1605884 13f79535-47bb-0310-9956-ffa450edef68
svn merge -c 1605892 FIXES: MAPREDUCE-5939. StartTime showing up as the epoch time in JHS UI after upgrade. Contributed by Chen He


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1605895 13f79535-47bb-0310-9956-ffa450edef68