LU-8585 tests: update sanity test for subdir mount

LU-8585 tests: update sanity test for subdir mount

Update the sanity test cases to pass when FILESET is set,
instead of skipping them.

Test-Parameters: trivial testlist=sanity
Signed-off-by: James Simmons <jsimmons@infradead.org>
Change-Id: Ie5eb429b80dbb89d3ee96515d503c57d107faa57
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/33666
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Reviewed-by: Arshad Hussain <arshad.hussain@aeoncomputing.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>