Bug 27927: Add Unit Tests

Bug 27927: Add Unit Tests

Add a unit test to check that 'FORGIVEN' credits do not prompt an
auto-renewal with `RenewAccruingItemWhenPaid` enabled.

Test plan
1/ Apply the test patch
2/ Run t/db_dependent/Koha/Account/Line.t and confirm it fails
3/ Apply subsequent patch
4/ Re-run the test and confirm it passes

Signed-off-by: Andrew Fuerste-Henry <andrew@bywatersolutions.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>