MAPREDUCE-5420. Remove mapreduce.task.tmp.dir from mapred-default.xml. Contributed by James Carman. (harsh)

(cherry picked from commit cb99f43305bd1577d4ba9527d237ac6cdb9ae730)
HDFS-7463. Simplify FSNamesystem#getBlockLocationsUpdateTimes. Contributed by Haohui Mai.
HDFS-7503. Namenode restart after large deletions can cause slow processReport (Arpit Agarwal)