Merge change r1550011 from trunk: Move HDFS-5257,HDFS-5427,HDFS-5443,HDFS-5476,HDFS-5425,HDFS-5474,HDFS-5504,HDFS-5428 into branch-2.3 section.

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HDFS-5074. Allow starting up from an fsimage checkpoint in the middle of a segment. Contributed by Todd Lipcon.


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Move entry for HDFS-5074 to correct section.


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Move HDFS-5283 to section branch-2.3.0

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HADOOP-10020. disable symlinks temporarily (cmccabe)

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