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?).
for pack_lot in ops.pack_lot_ids:
                    lot_qty[pack_lot.lot_id.id] = uom_obj._compute_qty(cr, uid, ops.product_uom_id.id, pack_lot.qty, ops.product_id.uom_id.id)
                for record in ops.linked_move_operation_ids.filtered(lambda x: x.move_id.id in main_domain):
                    move_qty = record.qty
                    move = record.move_id
                    domain = main_domain[move.id]
                    for lot in lot_qty:
                        if float_compare(lot_qty[lot], 0, precision_rounding=rounding) > 0 and float_compare(move_qty, 0, precision_rounding=rounding) > 0:
                            qty = min(lot_qty[lot], move_qty)
                            quants = quant_obj.quants_get_preferred_domain(cr, uid, qty, move, ops=ops, lot_id=lot, domain=domain, preferred_domain_list=[], context=context)
                            quant_obj.quants_reserve(cr, uid, quants, move, record, context=context)
                            lot_qty[lot] -= qty
                            move_qty -= qty
        
        
        todo_moves.sort(key=lambda x: -1 if ancestors_list.get(x.id) else 0)
        for move in todo_moves:
            
            if (move.state != 'assigned') and not context.get("reserve_only_ops"):
                qty_already_assigned = move.reserved_availability
                qty = move.product_qty - qty_already_assigned
                quants = quant_obj.quants_get_preferred_domain(cr, uid, qty, move, domain=main_domain[move.id], preferred_domain_list=[], context=context)
                quant_obj.quants_reserve(cr, uid, quants, move, context=context)
        
        
        if to_assign_moves:
            self.write(cr, uid, list(to_assign_moves), {'state': 'assigned'}, context=context)
        if not no_prepare:
            self.check_recompute_pack_op(cr, uid, ids, context=context)
    def action_cancel(self, cr, uid, ids, context=None):