Set picking type on PO generated from sourcing with FA

This bridge with onchanges on purchase_delivery_address
and make it consistant with purchase_requisition_delivery_address
I meant if it is a unittest I prefer to have one test by assert. The tests might be long at the end of the day but it is really helpful during debug I found.

I didn't realised that was not the case here and I understand why the test has so many  asserts.