HDFS-6355. Fix divide-by-zero, improper use of wall-clock time in BlockPoolSliceScanner (cmccabe)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1594339 13f79535-47bb-0310-9956-ffa450edef68
YARN-1861. Fixed a bug in RM to reset leader-election on fencing that was causing both RMs to be stuck in standby mode when automatic failover is enabled. Contributed by Karthik Kambatla and Xuan Gong.
svn merge --ignore-ancestry -c 1594356 ../../trunk/


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1594357 13f79535-47bb-0310-9956-ffa450edef68
YARN-1981. Nodemanager version is not updated when a node reconnects (Jason Lowe via jeagles)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1594361 13f79535-47bb-0310-9956-ffa450edef68
HDFS-6370. Merging change r1594362 from trunk to branch-2.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1594365 13f79535-47bb-0310-9956-ffa450edef68