Bug 19185: Fix regressions.t

Bug 19185: Fix regressions.t

The following test is failing:
| #   Failed test 'OPAC - Remove from cart'
| #   at t/db_dependent/selenium/regressions.t line 132.
| Can't call method "get_value" on an undefined value at t/db_dependent/selenium/regressions.t line 110.
| # Looks like your test exited with 2 just after 3.
| [12:14:08] t/db_dependent/selenium/regressions.t

We are dependind on the search engine and the records in the DB but the
installer is not inserting any records.

This patch is suggesting to reuse the code from search_utf8
(and so make it reusable first) for remove_from_cart test.
This code is mocking the Zebra index with some MARC data and so the
search will return results. We will finally be able to click on the
add to/remove from cart links.

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