HDFS-4503. Update computeContentSummary(..), spaceConsumedInTree(..) and diskspaceConsumed(..) in INode for snapshot.


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/HDFS-2802@1448373 13f79535-47bb-0310-9956-ffa450edef68