LU-15738 test: check lfsck status before starting

LU-15738 test: check lfsck status before starting

If the LFSCK has been started before calling "lfsck_start"
to start it, the test shouldn't fail for starting LFSCK.

Test-Parameters: trivial testlist=sanity-lfsck
Signed-off-by: Hongchao Zhang <hongchao@whamcloud.com>
Change-Id: I266d9e2b9c5f37eb9e08b489fab428268b90d895
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/48018
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Jian Yu <yujian@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>