svn merge -c 1609543 merging from trunk to branch-2 to fix:HDFS-6647. Edit log corruption when pipeline recovery occurs for deleted file present in snapshot. Contributed by Kihwal Lee.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1609544 13f79535-47bb-0310-9956-ffa450edef68