HDFS-6849. Replace HttpFS custom proxyuser handling with common implementation. (tucu)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1617833 13f79535-47bb-0310-9956-ffa450edef68
YARN-2277. Added cross-origin support for the timeline server web services. Contributed by Jonathan Eagles.
svn merge --ignore-ancestry -c 1617832 ../../trunk/


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1617834 13f79535-47bb-0310-9956-ffa450edef68
YARN-2070. Made DistributedShell publish the short user name to the timeline server. Contributed by Robert Kanter.
svn merge --ignore-ancestry -c 1617837 ../../trunk/


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1617839 13f79535-47bb-0310-9956-ffa450edef68