Steps to reproduce:
- create an expense product, re-invoice: "at cost"
- create a sale order with the product and set an analytic account
- create a purchase order with the expense product and the same analytic account
- create the bill
-> a new line on the SO is created with the same "Quantity Delivered" as the "Quantity Invoiced" for the purchase order
- for the bill, create a Credit Note of x unit
-> the purchase order has the Quantity Invoiced diminished of x

Issue:
- the Sale Order has not taken into account the new quantity after refund
- Since the line is an "analytic" one, the quantity delivered cannot be changed even if we wreate a credit note for the invoice

Solution:
During the processus of creation of new analytic lines, instead of creating new so lines we adapt the analytic line

closes odoo/odoo#115907

Signed-off-by: William André (wan) <wan@odoo.com>