HDFS-5372. In FSNamesystem, hasReadLock() returns false if the current thread holds the write lock (Contributed by Vinay)



git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1542887 13f79535-47bb-0310-9956-ffa450edef68
Merge remote-tracking branch: upstream/trunk