fix(controller): disable web UI

fixes #1144
fix(controller) disable django admin URL

If you accidentally create an object that requires an external library
such as the Release object, no docker image will be pushed to the registry,
which is unintentional. This disables the django admin URL such that you can't
shoot yourself in the :shoe:.
Merge pull request #1147 from deis/1114-disable-web

fix(controller): disable web UI from django urls