Bug 30588: (QA follow-up) Auth - remove two warns and second logout

Bug 30588: (QA follow-up) Auth - remove two warns and second logout

Resolves:
Use of uninitialized value $request_method in string eq at /usr/share/koha/C4/Auth.pm line 1122.
Use of uninitialized value $return in numeric gt (>) at /usr/share/koha/C4/Auth.pm line 1155.

We also remove the double logout from Auth.t

Test plan:
Run t/db_dependent/Auth.t
Check if you do not see the warns anymore.

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>