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?).
del quants_suggested_locations[quant]
        
        
        for quant, dest_location_id in quants_suggested_locations.items():
            key = (quant.product_id.id, quant.package_id.id, quant.owner_id.id, quant.location_id.id, dest_location_id)
            if qtys_grouped.get(key):
                qtys_grouped[key] += quant.qty
            else:
                qtys_grouped[key] = quant.qty
            if quant.product_id.tracking != 'none' and quant.lot_id:
                lots_grouped.setdefault(key, {}).setdefault(quant.lot_id.id, 0.0)
                lots_grouped[key][quant.lot_id.id] += quant.qty
        
        for product, qty in forced_qties.items():
            if qty <= 0:
                continue
            suggested_location_id = _picking_putaway_apply(product)
            key = (product.id, False, picking.owner_id.id, picking.location_id.id, suggested_location_id)
            if qtys_grouped.get(key):
                qtys_grouped[key] += qty
            else:
                qtys_grouped[key] = qty
        
        uom_obj = self.pool.get('product.uom')
        prevals = {}
        for key, qty in qtys_grouped.items():
            product = self.pool.get("product.product").browse(cr, uid, key[0], context=context)
            uom_id = product.uom_id.id
            qty_uom = qty
            if product_uom.get(key[0]):