Fix development-1 Varnish configuration

Varnish was failing with:

``` vagrant@dev-development-1:~$ sudo service varnish start
* Starting HTTP accelerator varnishd                                          
                                                                              
            [fail]  Message from VCC-compiler: Symbol not found:
'frontend_app' (expected type BACKEND):
('input' Line 46 Pos 25)
   set req.backend   = frontend_app;
------------------------############-

Running VCC-compiler failed, exit 1

VCL compilation failed
```