Merge r1592198 from branch-2: YARN-1201. TestAMAuthorization fails with local hostname cannot be resolved. (Wangda Tan via junping_du)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2.4@1592295 13f79535-47bb-0310-9956-ffa450edef68