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 procurement.rule_id.action == 'buy' and procurement.purchase_line_id:
                if procurement.purchase_line_id.order_id.state not in ('draft', 'cancel', 'sent', 'to validate'):
                    raise UserError(
                        _('Can not cancel a procurement related to a purchase order. Please cancel the purchase order first.'))
            if procurement.purchase_line_id:
                price_unit = 0.0
                product_qty = 0.0
                others_procs = procurement.purchase_line_id.procurement_ids.filtered(lambda r: r != procurement)
                for other_proc in others_procs:
                    if other_proc.state not in ['cancel', 'draft']:
                        product_qty += other_proc.product_uom._compute_quantity(other_proc.product_qty, procurement.purchase_line_id.product_uom)
                precision = self.env['decimal.precision'].precision_get('Product Unit of Measure')
                if not float_is_zero(product_qty, precision_digits=precision):
                    seller = procurement.product_id._select_seller(
                        partner_id=procurement.purchase_line_id.partner_id,
                        quantity=product_qty,
                        date=procurement.purchase_line_id.order_id.date_order and procurement.purchase_line_id.order_id.date_order[:10],
                        uom_id=procurement.purchase_line_id.product_uom)
                    price_unit = self.env['account.tax']._fix_tax_included_price_company(seller.price, procurement.purchase_line_id.product_id.supplier_taxes_id, procurement.purchase_line_id.taxes_id, procurement.company_id) if seller else 0.0
                    if price_unit and seller and procurement.purchase_line_id.order_id.currency_id and seller.currency_id != procurement.purchase_line_id.order_id.currency_id:
                        price_unit = seller.currency_id.compute(price_unit, procurement.purchase_line_id.order_id.currency_id)
                    if seller and seller.product_uom != procurement.purchase_line_id.product_uom:
                        price_unit = seller.product_uom._compute_price(price_unit, procurement.purchase_line_id.product_uom)
                    procurement.purchase_line_id.product_qty = product_qty
                    procurement.purchase_line_id.price_unit = price_unit
                else:
                    procurement.purchase_line_id.unlink()
        return result
    @api.multi
    def _run(self):