HDFS-6015. Fix TestBlockRecovery#testRaceBetweenReplicaRecoveryAndFinalizeBlock. Contributed by Kihwal Lee.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/HDFS-5535@1571785 13f79535-47bb-0310-9956-ffa450edef68