[FIX] delivery: Delivery Order Adding Freight Cost W/O Markup

Steps to reproduce the bug:

- Let's consider a delivery method DM with fixed price of 10€ and a margin of 20%
- Let's consider a storable product P
- Create a SO for P and get the rate (12€) but don't add it on the SO
- Confirm the SO and process the delivery

Bug:

A SO line was created for the freight cost without the margin. So it was 10€
instead of 12€.

opw:2144894

closes odoo/odoo#43279

X-original-commit: 621dac80
Signed-off-by: Simon Goffin (sig) <sig@openerp.com>