[FIX] stock_account: refund supplier invoice
[FIX] stock_account: refund supplier invoice

When Anglo-Saxon accounting is activated:
- Use two different accounts for Input/Output for Stock Valuation
- Create a vendor bill ==> by default, the Input Account for Stock
  Valuation is used
- Validate the vendor bill
- Refund the vendor bill

When the refund is created, the Output Account for Stock Valuation is
used. There is actually no obvious reason to use this account instead of
the account originally used.

opw-691571

Elico-Corp/odoo_OCB,hip-odoo/odoo,ygol/odoo,ygol/odoo,laslabs/odoo,laslabs/odoo,storm-computers/odoo,bplancher/odoo,Elico-Corp/odoo_OCB,bplancher/odoo,hip-odoo/odoo,Elico-Corp/odoo_OCB,laslabs/odoo,bplancher/odoo,Elico-Corp/odoo_OCB,ygol/odoo,dfang/odoo,laslabs/odoo,storm-computers/odoo,hip-odoo/odoo,dfang/odoo,Elico-Corp/odoo_OCB,bplancher/odoo,hip-odoo/odoo,Elico-Corp/odoo_OCB,laslabs/odoo,ygol/odoo,storm-computers/odoo,storm-computers/odoo,storm-computers/odoo,bplancher/odoo,hip-odoo/odoo,ygol/odoo,bplancher/odoo,laslabs/odoo,storm-computers/odoo,hip-odoo/odoo,dfang/odoo,ygol/odoo,dfang/odoo,ygol/odoo,dfang/odoo,dfang/odoo