HDFS-6325. Append should fail if the last block has insufficient number of replicas (Keith Pak via cos)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1595744 13f79535-47bb-0310-9956-ffa450edef68
MAPREDUCE-5867. Fix NPE in KillAMPreemptionPolicy related to ProportionalCapacityPreemptionPolicy. Contributed by Sunil G.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1595754 13f79535-47bb-0310-9956-ffa450edef68