Tests: Prevent DB commits
As a bonus, we can replace assertGreater ➔ assertEqual as our DB will no longer be polluted by remnants from previous test runs.
This does not apply to Odoo >= 13 where base.automation::_update_registry has been reworked to no longer reload the whole registry.
We also change partner.color to country.phone_code to match other similar modules.
--HG-- branch : 11.0