merge -c 1510805 FIXES: HADOOP-9832. [RPC v9] Add RPC header to client ping (daryn)


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2.1-beta@1510808 13f79535-47bb-0310-9956-ffa450edef68
MAPREDUCE-5399. Unnecessary Configuration instantiation in IFileInputStream slows down merge. (Stanislav Barton via Sandy Ryza)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2.1-beta@1510814 13f79535-47bb-0310-9956-ffa450edef68