MAPREDUCE-5268. Improve history server startup performance. Contributed by Karthik Kambatla


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1489012 13f79535-47bb-0310-9956-ffa450edef68
Move HADOOP-9397 to 2.1.0-beta after merging it into branch-2.


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1489026 13f79535-47bb-0310-9956-ffa450edef68