Bug 19300: Replace C4::Reserves::OPACItemHoldsAllowed - tests

Bug 19300: Replace C4::Reserves::OPACItemHoldsAllowed - tests

This patch proves that we will not introduce trivial regression.
With the same tests, we will execute the existing code and the new code.

Test plan:
With only this patch applied, prove t/db_dependent/Koha/IssuingRules.t
should return green

Followed test plan, patches worked as described
Signed-off-by: Alex Buckley <alexbuckley@catalyst.net.nz>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>