check: wipe scratch devices between tests

Wipe the scratch devices in between each test to ensure that tests are
formatting them and not making assumptions about previous contents.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Eryu Guan <guaneryu@gmail.com>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>
3 files changed