svn merge -c 1588949 merging from trunk to branch-2 to fix:HADOOP-10522. JniBasedUnixGroupMapping mishandles errors. Contributed by Kihwal Lee.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1588950 13f79535-47bb-0310-9956-ffa450edef68