HDFS-6227. ShortCircuitCache#unref should purge ShortCircuitReplicas whose streams have been closed by java interrupts. Contributed by Colin Patrick McCabe.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1597829 13f79535-47bb-0310-9956-ffa450edef68
HDFS-6416. Use Time#monotonicNow in OpenFileCtx and OpenFileCtxCatch to avoid system clock bugs. Contributed by Abhiraj Butala

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1597868 13f79535-47bb-0310-9956-ffa450edef68