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**
'default_model': 'purchase.order',
            'default_res_id': self.ids[0],
            'default_use_template': bool(template_id),
            'default_template_id': template_id,
            'default_composition_mode': 'comment',
        })
        return {
            'name': _('Compose Email'),
            'type': 'ir.actions.act_window',
            'view_type': 'form',
            'view_mode': 'form',
            'res_model': 'mail.compose.message',
            'views': [(compose_form_id, 'form')],
            'view_id': compose_form_id,
            'target': 'new',
            'context': ctx,
        }
    @api.multi
    def print_quotation(self):
        self.write({'state': "sent"})
        return self.env['report'].get_action(self, 'purchase.report_purchasequotation')
    @api.multi
    def button_approve(self, force=False):
        self.write({'state': 'purchase', 'date_approve': fields.Date.context_today(self)})
        self._create_picking()
        self.filtered(
            lambda p: p.company_id.po_lock == 'lock').write({'state': 'done'})
        return {}
    @api.multi
    def button_draft(self):