Merge r1607833 from Trunk: YARN-2251. Avoid negative elapsed time in JHS/MRAM web UI and services (Contributed by Zhijie Shen)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1607834 13f79535-47bb-0310-9956-ffa450edef68