Set same domain in wizard as on sale order to find po line to fill source_by field

We refer on the state of purchase order instead of purchase order line.
As purchase order state defines if moves have already been created or
not.
Merge pull request #72 from yvaucher/8.0-fix-sale_quotation_sourcing-domain-poline

8.0 Set same domain in wizard as on sale order to find po line to fill source_by field