[FIX] base: create user not from company_id=1

In new API conversion (7eab8e26d3) a SUPERUSER_ID was dropped hence
we could get an error instead of the default groups_id of a res.users (if
the user has no read permission for `default user`).

opw-687521

openerp/addons/base/res/res_users.py

@@ -181,7 +181,7 @@ class Users(models.Model):
 
     def _default_groups(self):
         default_user = self.env.ref('base.default_user', raise_if_not_found=False)
-        return (default_user or self.env['res.users']).groups_id
+        return (default_user or self.env['res.users']).sudo().groups_id
 
     def _companies_count(self):
         return self.env['res.company'].sudo().search_count([])