Fixes #17330 - skip admin email if it's unknown

When admin user is being seeded the Setting might not exist at that
moment. We can't just create it with value, since the setting would
be invalid because of other attributes. Therefore we split settings
creation from the setting list so we could create it from seed too.

This also fixes first_or_create calls that was broken by overrind the
create method. The setting was missing name since we didn't call new
method on Relation object.