svn merge -r 1595979:1595984 merging from branch-2 to branch-2.4 to fix:HDFS-6397. NN shows inconsistent value in deadnode count. Contributed by Mohammad Kamrul Islam.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2.4@1595986 13f79535-47bb-0310-9956-ffa450edef68