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?).
'product_ids': fields.many2many('product.template', 'stock_route_product', 'route_id', 'product_id', 'Products'),
        'categ_ids': fields.many2many('product.category', 'stock_location_route_categ', 'route_id', 'categ_id', 'Product Categories'),
        'warehouse_ids': fields.many2many('stock.warehouse', 'stock_route_warehouse', 'route_id', 'warehouse_id', 'Warehouses'),
    }
    _defaults = {
        'sequence': lambda self, cr, uid, ctx: 0,
        'active': True,
        'product_selectable': True,
        'company_id': lambda self, cr, uid, c: self.pool.get('res.company')._company_default_get(cr, uid, 'stock.location.route', context=c),
    }
    def write(self, cr, uid, ids, vals, context=None):
        '''when a route is deactivated, deactivate also its pull and push rules'''
        if isinstance(ids, (int, long)):
            ids = [ids]
        res = super(stock_location_route, self).write(cr, uid, ids, vals, context=context)
        if 'active' in vals:
            push_ids = []
            pull_ids = []
            for route in self.browse(cr, uid, ids, context=context):
                if route.push_ids:
                    push_ids += [r.id for r in route.push_ids if r.active != vals['active']]
                if route.pull_ids:
                    pull_ids += [r.id for r in route.pull_ids if r.active != vals['active']]
            if push_ids:
                self.pool.get('stock.location.path').write(cr, uid, push_ids, {'active': vals['active']}, context=context)
            if pull_ids:
                self.pool.get('procurement.rule').write(cr, uid, pull_ids, {'active': vals['active']}, context=context)
        return res
    def view_product_ids(self, cr, uid, ids, context=None):