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**
_inherit = "product.category"
    property_account_creditor_price_difference_categ = fields.Many2one(
        'account.account', string="Price Difference Account",
        company_dependent=True,
        help="This account will be used to value price difference between purchase price and accounting cost.")
class MailComposeMessage(models.TransientModel):
    _inherit = 'mail.compose.message'
    @api.multi
    def mail_purchase_order_on_send(self):
        if not self.filtered('subtype_id.internal'):
            order = self.env['purchase.order'].browse(self._context['default_res_id'])
            if order.state == 'draft':
                order.state = 'sent'
    @api.multi
    def send_mail(self, auto_commit=False):
        if self._context.get('default_model') == 'purchase.order' and self._context.get('default_res_id'):
            self = self.with_context(mail_post_autofollow=True)
            self.mail_purchase_order_on_send()
        return super(MailComposeMessage, self).send_mail(auto_commit=auto_commit)