Wrong account for invoice lines created from delivery for service products

Version 6.0.1

When a invoices is created from a delivery in the sales flow with shipping policy "Invoice from Delivery" the wrong account is used for services products.

Steps to reproduce:
1) Create a new SO
2) Add a stockable and a service product to the SO
3) Select shipping policy "Invoice from Delivery"
4) Go the delivery and create the invoice
6) Open the generated invoice

Result observed:
The account used for the service product invoice line is wrong, the one used for the stockable product is correct. The account set in property_account_expense is used for the service product.

Expeted result:
The account set in property_account_receivable should be used.

Potential problem solution:
Function action_invoice_create in addons/sale/stock.py does not care on the invoice type as done in inherited method action_invoice_create in addons/stock/stock.py line 978. As the type has the value "None" the sale_line.product_id.product_tmpl_id.property_account_expense.id is used on line 157.

Either use the value set in the context ('inv_type') or use the function self._get_invoice_type(picking) as done in addons/stock/stock.py line 978.