LU-4808 tests: don't skip sanity test_116b incorrectly

LU-4808 tests: don't skip sanity test_116b incorrectly

An exception was added in http://review.whamcloud.com/9766 (commit
e217648d50da) to skip sanity test_116b if running against an MDS
that does not have the qos_threshold_rr tunable, but this was
incorrectly checking the local (client) for the tunable instead of
the MDS.  Fix the check to run on the MDS.

Signed-off-by: Andreas Dilger <andreas.dilger@intel.com>
Change-Id: Ia1ae05373af9e92d91710761f1da6470f8500c1e
Reviewed-on: http://review.whamcloud.com/13263
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Jian Yu <jian.yu@intel.com>
Reviewed-by: Dmitry Eremin <dmitry.eremin@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>