LU-18162 kunit: convert OBD test to LU device

LU-18162 kunit: convert OBD test to LU device

Convert OBD test to use LU device init/fini rather
than the legacy OBD API.

Test-Parameters: trivial testlist=sanity env=ONLY=55,ONLY_REPEAT=25
Signed-off-by: Timothy Day <timday@amazon.com>
Change-Id: Idd7f31fdf6daebfad448bed9c4ca7102f45c1688
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/58785
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Arshad Hussain <arshad.hussain@aeoncomputing.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>