text: Title: forms.MultipleChoiceField doesn't work as it does in default admin site
  Body: When a use django default admin site, I get the desired MultiChoiceField 
  ![default admin](https://user-images.githubusercontent.com/22144491/39010646-f35f9182-442e-11e8-8ea4-9114e295d6b6.png)
  
  but when i switch to django-jet admin site I get something like below, none of the option are selectable
  ![django-jet](https://user-images.githubusercontent.com/22144491/39010685-17032586-442f-11e8-83d6-4aa72e767b0c.png)
  
  