[FIX] point_of_sale: show the promotion line for the refund

Before this commit: if you wanted to refund an order that contains a
promotion line, it did not show the promotion line to refund. The
problem was that, during the initialization of an order from JSON, it
calls `set_partner` and `set_pricelist`. It causes a call to
`_updateRewards()` inside the `pos_loyalty`, which will remove the
promotion line. But it doesn't need to update the rewards when it
creates the order object from JSON.

The solution is to prevent calling `set_partner` and `set_pricelist`
when it creates the order object from the JSON.

opw-3111578

closes odoo/odoo#114982

Signed-off-by: Trinh Jacky (trj) <trj@odoo.com>