Bug 14342: Unit tests in t/db_dependent/Context.t failing due to Bug 13967

Bug 14342: Unit tests in t/db_dependent/Context.t failing due to Bug 13967

The introduction of system preference objects in bug 13967 has caused
the current testing regimen to fail do to the mixing of DBI mocking and
DBIx::Class.

Test Plan:
1) Apply this patch
2) prove t/db_dependent/Context.t

Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>