tests/sys/cddl/zfs/tests/snapshot/snapshot_019_pos.ksh:

• Significantly increase the aggressiveness of this test:
  • Before each stat call on $SNAPDIR, cd to $SNAPDIR. This tests the

	  ability of the system to properly move process references.

• Add a new "thread" that runs "ls $SNAPDIR/.." as fast as possible.

	  This effectively forces the kernel to obtain the currently mounted
	  snapshot filesystem's root vnode, mounting if necessary, and
	  *then* use that vnode to lookup (and lock) its parent.

• In addition to doing non-forced unmounts on $SNAPDIR, also do

	  forced unmounts.

• Finally, when the unmount loop ends, signal the "threads" to exit

	  and wait for them to die.  Then require a *non-forced* unmount of
	  the filesystem, which tests for leaked references.

Submitted by: Will
Sponsored by: Spectra Logic Corp