HADOOP-10169. Remove the unnecessary synchronized in JvmMetrics class. Contributed by Liang Xie.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1552820 13f79535-47bb-0310-9956-ffa450edef68
HDFS-2933. Fix incorrect target version in CHANGES.txt

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1552837 13f79535-47bb-0310-9956-ffa450edef68
HDFS-5636. Enforce a max TTL per cache pool (awang via cmccabe)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1552841 13f79535-47bb-0310-9956-ffa450edef68