LU-7668 tests: skip conf-sanity test_33a for old MGS

LU-7668 tests: skip conf-sanity test_33a for old MGS

Skip del_ost test for MGS versions that do not have this command.

Test-Parameters: trivial
Test-Parameters: testlist=conf-sanity env=ONLY="33a 123ah" serverversion=2.15.0
Fixes: 1121816c4a ("LU-7668 utils: add lctl del_ost")
Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Change-Id: Ib8ca9c604404e5717533be32fd6b5ccfbf70428e
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/50221
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Alex Deiter <alex.deiter@gmail.com>
Reviewed-by: Sarah Liu <sarah@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>