HDFS-7180. NFSv3 gateway frequently gets stuck due to GC. Contributed by Brandon Li

(cherry picked from commit d71d40a63d198991077d5babd70be5e9787a53f1)

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

(cherry picked from commit d27cd5ad771d640b470aabe66c7fbddd508a2967)