HDFS-4882. Prevent the Namenode's LeaseManager from looping forever in checkLeases (Ravi Prakash via Colin P. McCabe)
(cherry picked from commit daacbc18d739d030822df0b75205eeb067f89850)
HDFS-7419. Improve error messages for DataNode hot swap drive feature (Lei Xu via Colin P. Mccabe)
(cherry picked from commit f636f9d9439742d7ebaaf21f7e22652403572c61)
HDFS-7412. Move RetryCache to NameNodeRpcServer. Contributed by Haohui Mai.