HDFS-5385. Caching RPCs are AtMostOnce, but do not persist client ID and call ID to edit log.  (Chris Nauroth via Colin Patrick McCabe)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/HDFS-4949@1534345 13f79535-47bb-0310-9956-ffa450edef68