HDFS-5438. Flaws in block report processing can cause data loss. Contributed by Kihwal Lee.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-0.23@1542058 13f79535-47bb-0310-9956-ffa450edef68
HADOOP-9955. RPC idle connection closing is extremely inefficient (daryn)


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-0.23@1542113 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-HADOOP-9281-branch-0.23-gd