MAPREDUCE-5844. Add a configurable delay to reducer-preemption. (Maysam Yabandeh via kasha)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1604032 13f79535-47bb-0310-9956-ffa450edef68
HDFS-6312. WebHdfs HA failover is broken on secure clusters. (daryn via tucu)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1604046 13f79535-47bb-0310-9956-ffa450edef68
HDFS-6403. Add metrics for log warnings reported by JVM pauses. Contributed by Yongjun Zhang.


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1604076 13f79535-47bb-0310-9956-ffa450edef68