change djfs settings not to throw an error when the app starts up

@singingwolfboy  
@feanil 

Can we merge this in so that sandbox builds don't fail? 
http://jenkins.edx.org:8080/job/connect-sandbox-to-prod-clone/122/console
This should be on two lines.
```python
if 'DJFS' in AUTH_TOKENS:
    DHFS = AUTH_TOKENS['DJFS']
```