YARN-1188. The context of QueueMetrics becomes default when using FairScheduler (Akira Ajisaka via Sandy Ryza)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1525516 13f79535-47bb-0310-9956-ffa450edef68
Fix credit for YARN-1188

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1525518 13f79535-47bb-0310-9956-ffa450edef68
Merge remote-tracking branch: upstream/trunk