[FIX] stock: validate an immediate transfer without a backorder

Steps to reproduce the bug:
- Create a Storable product “C1” tracked by Lot:
    - Update the Qty to 10

- Create a Storable product “P1”:
    - Add a BoM:
        - add 1 unit of  “C1” as component

- Enable 3 steps for the manufacturing operation in warehouse settings

- Create a Mo to produce 1 unit of “P1”:
    - Confirm the MO
    - Click on related transfer:
        - Select the “Pick component”
        - check that the qty is reserved correctly
        - Try to validate it without setting Qty done
        - The immediate transfer is triggered, validate it

Problem:
The backorder's wizard triggers when it shouldn't

To know if we should create a backorder, we check if the qty reserved
is equal to the qty done, and as the qty done was not set correctly
during the validation of the immediate transfer, the two quantities
are not identical, therefore the widget is trigger:

https://github.com/odoo/odoo/blob/15.0/addons/stock/models/stock_picking.py#L1128-L1132



opw-3240264

closes odoo/odoo#116196

Signed-off-by: Steve Van Essche <svs@odoo.com>