HADOOP-9919. Update hadoop-metrics2.properties examples to Yarn. Contributed by Akira AJISAKA.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1588943 13f79535-47bb-0310-9956-ffa450edef68
HADOOP-10522. JniBasedUnixGroupMapping mishandles errors. Contributed by Kihwal Lee.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1588949 13f79535-47bb-0310-9956-ffa450edef68