[FIX] mrp: update unit_factor when updating MO quantity
[FIX] mrp: update unit_factor when updating MO quantity

Set a BOM to create 10^k units of Product P, using n units of raw material R.
On R, put rounding to 1 unit.
Create a MO to produce 1 unit of P.
Since it needs n/10^k units and rounding is set to 1,
it sets 1 unit of R to consume.
Now "update" (quantity to produce) to 10^k'.
It correctly updates the quantity to consume.
However, since it doesn't update the unit_factor, when you "produce",
it will consume 10^k' units instead of 1.

We copy the way the unit_factor is initially computed when updating the lines.

opw 1903776

closes odoo/odoo#29067
ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo