MAPREDUCE-5966. MR1 FairScheduler use of custom weight adjuster is not thread safe for comparisons. (Anubhav Dhoot via kasha)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-1@1613720 13f79535-47bb-0310-9956-ffa450edef68