HDFS-5257. addBlock() retry should return LocatedBlock with locations else client will get AIOBE. Contributed by Vinay.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1535811 13f79535-47bb-0310-9956-ffa450edef68
Merge remote branch 'origin/trunk' into trunk-gd