LU-4747 tests: Call get_param from MDS

LU-4747 tests: Call get_param from MDS

In sanity tests 120a, b, c, d, e, f and g,
"lctl get_param ldlm.services.ldlm_canceld.stats" is
called from the client, but these stats are only
on the MDS.

Adding do_facet to the MDS gets the necessary stats.

Signed-off-by: James Nunez <james.a.nunez@intel.com>
Change-Id: I6b8434960bf5ec5e1220460612a583f2ab763980
Reviewed-on: http://review.whamcloud.com/9581
Tested-by: Jenkins
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Jian Yu <jian.yu@intel.com>