MAPREDUCE-5822. FairScheduler does not preempt due to fairshare-starvation when fairshare is 1. (Anubhav Dhoot via kasha)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-1@1586784 13f79535-47bb-0310-9956-ffa450edef68