Bug 26589: Fix t/db_dependent/OAI/Sets.t failing when OAI-PMH:AutoUpdateSets is enabled

Bug 26589: Fix t/db_dependent/OAI/Sets.t failing when OAI-PMH:AutoUpdateSets is enabled

Test plan:
1. Check the OAI-PMH:AutoUpdateSets syspref is disabled
2. Run t/db_dependent/OAI/Sets.t tests and confirm tests pass
successfully
3. Enabled the OAI-PMH:AutoUpdateSets syspref
4. Repeat step 2 and confirm the tests fail

5. Apply this patch and restart plack: sudo koha-plack --restart
<instance>
6. Repeat step 2 and confirm the tests now pass
7. Disable the OAI-PMH:AutoUpdateSets syspref and repeat step 2 and
confirm tests still pass

Sponsored-By: Catalyst IT
Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>