Bug 31557: (QA follow-up) Make tests more robust
Tests had a few problems:
- They weren't wrapped in a transaction explicitly
- They called Koha::Biblios->delete!
- They failed if run a couple times
This patch:
- Wraps things in a transaction
- Removes not-required things ($target_rs variable not used)
- Preserves the tests logic, but filters the resultset on the
biblionumber instead of deleting all the database which can fail
depending on FK constraints.
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>