HDFS-7215.Add JvmPauseMonitor to NFS gateway. Contributed by Brandon Li

(cherry picked from commit 4e134a02a4b6f30704b99dfb166dc361daf426ea)

Conflicts:
	hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt

(cherry picked from commit c800e058ea023a6fa8b68a0cf797c8aa0e2d9226)