[FIX] point_of_sale, product, sale: Manage pricelist items

Steps to reproduce the bug:

- Let's consider that Sales and Point of sale modules are installed
- Go to Sales > Settings and check "Multiple Sales Prices per Product"
- Select "Prices computed from formulas (discounts, margins, roundings)"
- Let the default setting for "Multiple Sales Prices per Product" in Point of sale settings
- Go to Website > Settings and change the domain url of your website
- Save

Bug:

The pricelist items didn't appear in the pricelist even if the option
Select Prices computed from formulas (discounts, margins, roundings) was
selected in Sales module.

Explanations:

Each time a save was made in the settings, the setting of "Multiple Sales Prices per Product"
from Point of sales were applied after the settings of Sales. So there was an inconsistency.

opw:2240068

closes odoo/odoo#50435

Signed-off-by: Simon Goffin (sig) <sig@openerp.com>