HDFS-4774. Backport HDFS-4525: Provide an API for knowing whether a file is closed.  Contributed by Ted Yu


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HADOOP-9543. TestFsShellReturnCode may fail if the hardcoded user "admin" is not a valid user in the loacl OS.


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-1@1478524 13f79535-47bb-0310-9956-ffa450edef68