HDFS-4482. ReplicationMonitor thread can exit with NPE due to the race between delete and replication of same file. Contributed by Uma Maheswara Rao G.



git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1448708 13f79535-47bb-0310-9956-ffa450edef68
Merge remote branch 'origin/trunk' into trunk-gd
Merge remote branch 'origin/trunk-gd' into fb-HDFS-4312-trunk-gd