LU-6106 test: skip test_16 to test_23 if MDS version older than 2.6.90

LU-6106 test: skip test_16 to test_23 if MDS version older than 2.6.90

Skip sanity-sec test_16 to test_23 if MDS version older than 2.6.90.
The previous commit 0f95dae3a7a0bdef52160a3ca76fefac6765007c doesn't
prevent the tests from being run, fix the problem in this one.

Change-Id: I791f1e81c248979270524d57305e545f388a9d67
Signed-off-by: Wei Liu <wei3.liu@intel.com>
Reviewed-on: http://review.whamcloud.com/13806
Tested-by: Jenkins
Reviewed-by: Jian Yu <jian.yu@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>