Bug 30571: Z3950Servers.t - Create subtest for existing tests

Bug 30571: Z3950Servers.t - Create subtest for existing tests

No real changes, just moving code and indentation.
Ground work for following patch.

Test plan:
To let the test pass, disable strict_mode in koha-conf.
Run perl t/db_dependent/Koha/Z3950Servers.t. Should pass now.
However, in strict mode or with prove, it should fail.
Run prove t/db_dependent/Koha/Z3950Servers.t. Failed?

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>