MAPREDUCE-5280. Bring back removed constructor and a method in mapreduce ClusterMetrics for binary compatibility with 1.x APIs. Contributed by Mayank Bansal.
svn merge --ignore-ancestry -c 1488458 ../../trunk/


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1488459 13f79535-47bb-0310-9956-ffa450edef68