LU-3689 tests: Support ZFS in large-lun.sh and run_llverdev

LU-3689 tests: Support ZFS in large-lun.sh and run_llverdev

This adds support to "check" zfs and run llrevfs against zfs backed
nodes.  This fixes some regressions added by LU-3264, specifically
that the stop function also exports the zfs pool.

The zfs "check" is really a non-entity since there is no functional
zfs fsck at this time.

Test-Parameters: mdsfilesystemtype=zfs mdtfilesystemtype=zfs ostfilesystemtype=zfs testlist=large-lun ostcount=2 envdefinitions=SLOW=yes
Signed-off-by: Nathaniel Clark <nathaniel.l.clark@intel.com>
Change-Id: Idc35d35152f1cbdc4afe6a0f627a5c1ba40b3faf
Reviewed-on: http://review.whamcloud.com/7395
Tested-by: Jenkins
Reviewed-by: Jian Yu <jian.yu@intel.com>
Reviewed-by: Wei Liu <wei3.liu@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Bob Glossman <bob.glossman@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>