LU-18109 tests: skip sanity-sec test_27ab for old MDS

LU-18109 tests: skip sanity-sec test_27ab for old MDS

The nodemap offset functionality was only added for MDS versions
after 2.16.0-170, so should be skipped for older versions.

Test-Parameters: trivial
Test-Parameters: testlist=sanity-sec env=ONLY=27ab serverversion=2.15
Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Change-Id: Ie0ac0e419b9bb94dee24fc12e135081a6eb7440c
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/57555
Tested-by: Oleg Drokin <green@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>