Impacted versions:
* 11.0

Steps to reproduce:
* Create company A
* Create company B
* Admin user with both companies but currently in company B
* Create Demo user only with company B
* Create fiscal position A to company A
* Create fiscal position B to company B
* Create vendor with fiscal position A with company A and the same vendor with fiscal position B in company B
* Create product and add the vendor created before
* Set like **Create a draft purchase order**
* Logging with Demo user
* Create sale order with one sale order line with route **make to order**
* Validate sale order

Current behavior:
The purchase order created by sale order has the fiscal position **company A**

Expected behavior:
The purchase order must have fiscal position **company B**
if (self.state == 'purchase' or self.state == 'to approve') and self.product_id.type in ['product', 'consu'] and self.product_qty < self._origin.product_qty:
            warning_mess = {
                'title': _('Ordered quantity decreased!'),
                'message' : _('You are decreasing the ordered quantity!\nYou must update the quantities on the reception and/or bills.'),
            }
            return {'warning': warning_mess}
    def _suggest_quantity(self):
        '''
        Suggest a minimal quantity based on the seller
        '''
        if not self.product_id:
            return
        seller_min_qty = self.product_id.seller_ids\
            .filtered(lambda r: r.name == self.order_id.partner_id)\
            .sorted(key=lambda r: r.min_qty)
        if seller_min_qty:
            self.product_qty = seller_min_qty[0].min_qty or 1.0
            self.product_uom = seller_min_qty[0].product_uom
        else:
            self.product_qty = 1.0
class ProcurementRule(models.Model):