HDFS-4749. Use INodeId to identify the corresponding directory node in FSImage saving/loading.  Contributed by Jing Zhao


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/HDFS-2802@1475902 13f79535-47bb-0310-9956-ffa450edef68
HDFS-4742. Fix appending to a renamed file with snapshot.  Contributed by Jing Zhao


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/HDFS-2802@1475903 13f79535-47bb-0310-9956-ffa450edef68