HDFS-4577. Webhdfs operations should declare if authentication is required. Contributed by Daryn Sharp.

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svn merge -c 1205697 Merging from trunk to branch-0.23 to fix HADOOP-7358.

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svn merge -c 1375790 Merging from trunk to branch-0.23 to fix HADOOP-8711.

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svn merge -c 1376054 Merging from truk to branch-0.23 to fix HDFS-3817.

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