LU-9260 test: Use the correct mount device when test against lustre

LU-9260 test: Use the correct mount device when test against lustre

The changes pass the MGSNID:/FSNAME into test, instead of
using the default loop device when testing against lustre.
The corresponding changes to the Posix test suites are also needed
to make the testing pass. Related changes apply to toolkit.

Test-Parameters: trivial testlist=posix

Change-Id: I32fc5a401fdc53ed133a78dc4c84b4a7e2a5ad19
Signed-off-by: Wei Liu <wei3.liu@intel.com>
Reviewed-on: https://review.whamcloud.com/28661
Reviewed-by: Jian Yu <jian.yu@intel.com>
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: James Nunez <james.a.nunez@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>