HDFS-4806. In INodeDirectoryWithSnapshot, use isInLatestSnapshot() to determine if an added/removed child should be recorded in the snapshot diff.  Contributed by Jing Zhao


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/HDFS-2802@1480146 13f79535-47bb-0310-9956-ffa450edef68