Feature/disable password login cont

WP [#7626](https://www.openproject.org/work_packages/7626)
I don't like this way of checking as it breaks if the default settings by coincidence equal the value here. That's not probable, but we can't be sure. Also, the tests doesn't actuallly check that the value doesn't change, it only checks the setting does not have the new value.

I'd rather set a specific value before running the tests and check for that value here. You're restoring the original values anyway, so this shouldn't be too much work.