HDFS-5936. MiniDFSCluster does not clean data left behind by SecondaryNameNode. Contributed by Binglin Chang.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1572150 13f79535-47bb-0310-9956-ffa450edef68
HDFS-6018. Exception recorded in LOG when IPCLoggerChannel#close is called. Contributed by Jing Zhao.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1572183 13f79535-47bb-0310-9956-ffa450edef68
HDFS-4685. Move to 2.4.0 in CHANGES.txt in preparation for merge.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1572189 13f79535-47bb-0310-9956-ffa450edef68
HADOOP-10184. Move to 2.4.0 in CHANGES.txt in preparation for merge.

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Merge remote-tracking branch: upstream/trunk