svn merge -c 1593475 merging from trunk to branch-2 to fix:HDFS-6313. WebHdfs may use the wrong NN when configured for multiple HA NNs. Contributed by Kihwal Lee.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1593476 13f79535-47bb-0310-9956-ffa450edef68