selftests: ublk: fix test_stripe_04

Commit 57ed58c1 ("selftests: ublk: enable zero copy for stripe target")
added test entry of test_stripe_04, but forgot to add the test script.

So fix the test by adding the script file.

Reported-by: Uday Shankar <ushankar@purestorage.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Uday Shankar <ushankar@purestorage.com>
Link: https://lore.kernel.org/r/20250404001849.1443064-1-ming.lei@redhat.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>