HDFS-4882. Prevent the Namenode's LeaseManager from looping forever in checkLeases (Ravi Prakash via Colin P. McCabe)
HDFS-7419. Improve error messages for DataNode hot swap drive feature (Lei Xu via Colin P. Mccabe)
HDFS-7412. Move RetryCache to NameNodeRpcServer. Contributed by Haohui Mai.