Bug 18070: Deleting an authority should update the linked biblio records

Bug 18070: Deleting an authority should update the linked biblio records

Adding a test where we delete an authority and prove that the linked
biblio still contains a reference to it.

Note: Currently, you can only delete a used authority from Tools,
batch record deletion. If you do, the biblio records will still
contain references to the deleted authority.

Test plan:
[1] Run t/db_dependent/Authorities/Merge.t
    Last test should fail: not ok 1 - Field 609 should be gone too

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Josef Moravec <josef.moravec@gmail.com>
Signed-off-by: Julian Maurice <julian.maurice@biblibre.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>