Bug 36084: Fix cookie domain for www/ tests

Bug 36084: Fix cookie domain for www/ tests

This patch changes the hardcoded `koha.local` value on
t::lib::Mocks::Zebra so tests don't fail when the domain is not `koha`.

To test:
1. Run:
   $ ktd --shell
  k$ export KOHA_INTRANET_URL=http://kohadev-intra.myDNSname.org:8081
  k$ prove t/db_dependent/www/batch.t
=> FAIL: Tests fail!
2. Apply this patch
3. Repeat 1
=> SUCCESS: Tests pass!
4. Sign off :-D

Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>