[FIX] auth_signup: send confirmation email when registering

Steps to reproduce:
- In settings, activate "Free sign up" option;
- Go to "Sign in" page;
- Click on "Don't have an account?";
- Create an account.

Issue:
No confirmation email is sent.

Cause:
The `qcontext.get('token')` variable does not exist
in the case of a "Free sign up".
And therefore, we do not respect the condition to send an email.

opw-3103867

closes odoo/odoo#111939

X-original-commit: ad95fbdd
Signed-off-by: Martin Trigaux (mat) <mat@odoo.com>
Signed-off-by: Thibault Delavallee (tde) <tde@openerp.com>