HDFS-4842. Identify the correct prior snapshot when deleting a snapshot under a renamed subtree. Contributed by Jing Zhao.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1487643 13f79535-47bb-0310-9956-ffa450edef68
HDFS-4846. Clean up snapshot CLI commands output stacktrace for invalid arguments. Contributed by Jing Zhao

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1487647 13f79535-47bb-0310-9956-ffa450edef68
HDFS-4857. Snapshot.Root and AbstractINodeDiff#snapshotINode should not be put into INodeMap when loading FSImage. Contributed by Jing Zhao

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1487655 13f79535-47bb-0310-9956-ffa450edef68
Merge remote branch 'origin/trunk' into trunk-gd
Merge remote branch 'origin/trunk-gd' into fb-HADOOP-7435-TEST-trunk-gd