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?).
"""
            Returns warehouse id of warehouse that contains location
            :param location: browse record (stock.location)
        """
        wh_obj = self.pool.get("stock.warehouse")
        whs = wh_obj.search(cr, uid, [('view_location_id.parent_left', '<=', location.parent_left), 
                                ('view_location_id.parent_right', '>=', location.parent_left)], context=context)
        return whs and whs[0] or False
class stock_location_route(osv.osv):
    _name = 'stock.location.route'
    _description = "Inventory Routes"
    _order = 'sequence'
    _columns = {
        'name': fields.char('Route Name', required=True, translate=True),
        'sequence': fields.integer('Sequence'),
        'pull_ids': fields.one2many('procurement.rule', 'route_id', 'Procurement Rules', copy=True),
        'active': fields.boolean('Active', help="If the active field is set to False, it will allow you to hide the route without removing it."),
        'push_ids': fields.one2many('stock.location.path', 'route_id', 'Push Rules', copy=True),
        'product_selectable': fields.boolean('Applicable on Product', help="When checked, the route will be selectable in the Inventory tab of the Product form.  It will take priority over the Warehouse route. "),
        'product_categ_selectable': fields.boolean('Applicable on Product Category', help="When checked, the route will be selectable on the Product Category.  It will take priority over the Warehouse route. "),
        'warehouse_selectable': fields.boolean('Applicable on Warehouse', help="When a warehouse is selected for this route, this route should be seen as the default route when products pass through this warehouse.  This behaviour can be overridden by the routes on the Product/Product Categories or by the Preferred Routes on the Procurement"),
        'supplied_wh_id': fields.many2one('stock.warehouse', 'Supplied Warehouse'),
        'supplier_wh_id': fields.many2one('stock.warehouse', 'Supplying Warehouse'),
        'company_id': fields.many2one('res.company', 'Company', select=1, help='Leave this field empty if this route is shared between all companies'),