Merge HDFS-5343. When cat command is issued on snapshot files, getting unexpected result. Contributed by Sathish.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1561326 13f79535-47bb-0310-9956-ffa450edef68
HDFS-5719. FSImage#doRollback() should close prevState before return. Contributed by Ted Yu.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1561388 13f79535-47bb-0310-9956-ffa450edef68
HDFS-5721. sharedEditsImage in Namenode#initializeSharedEdits() should be closed before method returns. Contributed by Ted Yu.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1561389 13f79535-47bb-0310-9956-ffa450edef68