HADOOP-9686. Easy access to final parameters in Configuration (Jason Lowe via jeagles)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1516009 13f79535-47bb-0310-9956-ffa450edef68
HADOOP-9886. Merging change r1516034 from trunk

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1516038 13f79535-47bb-0310-9956-ffa450edef68