[FIX] sale_crm: always create a new customer when create is selected

When clicking on the 'New quotation' action,
if no current customer is linked to the lead,
a popup opens with the following options:
- Create a new customer
- Link to an existing customer
- Do not link to a customer

If odoo found a potential matching customer but we decide it is the
wrong one and select the first option, a new one should always be
created

opw-2545065
Task-2622793

closes odoo/odoo#74988

Signed-off-by: Thibault Delavallee (tde) <tde@openerp.com>