MAPREDUCE-5585. TestCopyCommitter#testNoCommitAction Fails on JDK7 (jeagles)

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MAPREDUCE-5586. TestCopyMapper#testCopyFailOnBlockSizeDifference fails when run from hadoop-tools/hadoop-distcp directory (jeagles)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-0.23@1532896 13f79535-47bb-0310-9956-ffa450edef68
HDFS-5346. Avoid unnecessary call to getNumLiveDataNodes() for each block during IBR processing. Contributed by Ravi Prakash.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-0.23@1532917 13f79535-47bb-0310-9956-ffa450edef68
Merge remote branch 'origin/branch-0.23' into branch-0.23-gd
Merge remote branch 'origin/branch-0.23-gd' into fb-YAHOO-275-branch-0.23-gd