Impacted versions: 9.0

Steps to reproduce:

* Create an MTO product with 
  * Product Type: Stockable Product
  * Routes: "Buy" and "Make to Order"
* Update Qty on Hand to any quantity (i.e, 2).
* Create a sales order with this product and a number <= to the one in the step before.
* Confirm the sales order.

Current behavior:

The created delivery picking appears in state "Reserved" and the current quantity on stock has been reserved, allowing you to transfer that stock.

Expected behavior:

The created delivery picking should be in "Waiting another operation", or at least in "Waiting availability" until the purchase order is confirmed (if you have defined a supplier for the product and the procurement creates the purchase order), which seems to be the current behavior when there's no stock available (is this also correct, as it allows to manually reserve?).
res = {}
        for pack in self.browse(cr, uid, ids, context=context):
            res[pack.id] = (pack.qty_done > 0.0)
        return res
    def _set_processed_qty(self, cr, uid, id, field_name, field_value, arg, context=None):
        op = self.browse(cr, uid, id, context=context)
        if not op.product_id:
            if field_value and op.qty_done == 0:
                self.write(cr, uid, [id], {'qty_done': 1.0}, context=context)
            if not field_value and op.qty_done != 0:
                self.write(cr, uid, [id], {'qty_done': 0.0}, context=context)
        return True
    def _compute_lots_visible(self, cr, uid, ids, field_name, arg, context=None):
        res = {}
        for pack in self.browse(cr, uid, ids, context=context):
            if pack.pack_lot_ids:
                res[pack.id] = True
                continue
            pick = pack.picking_id
            product_requires = (pack.product_id.tracking != 'none')
            if pick.picking_type_id:
                res[pack.id] = (pick.picking_type_id.use_existing_lots or pick.picking_type_id.use_create_lots) and product_requires
            else:
                res[pack.id] = product_requires
        return res
    def _get_default_from_loc(self, cr, uid, context=None):