LU-6468 tests: skip conf-sanity.sh test_83 for 2.6.90 or older

LU-6468 tests: skip conf-sanity.sh test_83 for 2.6.90 or older

Skip conf-sanity.sh test_83 if OST server version is older than
2.6.91.

Test-Parameters: alwaysuploadlogs testlist=conf-sanity envdefinitions=ONLY=83 ossjob=lustre-b2_5 mdsjob=lustre-b2_5 ossbuildno=86 mdsbuildno=86
Signed-off-by: Emoly Liu <emoly.liu@intel.com>
Change-Id: I38fe3a52586dcb4d5706b4d7c379685e09e031cc
Reviewed-on: http://review.whamcloud.com/14534
Tested-by: Jenkins
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Jian Yu <jian.yu@intel.com>