Angularjs，无法设置从数据库返回的json对象的下拉列表

I have a customer dropdown with nested json and saving the selected customer json object in the data base and retrieving it in the same format. Now when I set back the selected customer model with the retrieved json object, the customer drop is not getting selected to this new one and the drop down remains unselected. Please find the plunker at I have a customer dropdown with nested json and