Bug 15333: [QA Follow-up] Add few tests

Bug 15333: [QA Follow-up] Add few tests

This report had no test plan and no unit tests.
Adding some lines to Holidays.t.
Added a trivial line move in Calendar.pm.

Test plan:
Run t/db_dependent/Holidays.t with and without cache.

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Tested with memcached, Cache::Memory and no cache (edit Cache.pm).

Signed-off-by: Brendan Gallagher <brendan@bywatersolutions.com>
(cherry picked from commit 73aa490029b4b536c86c3ac59e53f9e118c7c292)
Signed-off-by: Julian Maurice <julian.maurice@biblibre.com>