Code review comment for lp://staging/~dpniel/ubuntu-autopilot-tests/test-runner

I'm curious about desktop-autopilot-runner/custom-installation/iso-override/etc/apt/sources.list

deb http://archive.ubuntu.com/ubuntu/ trusty main restricted universe multiverse

We're pushing trusty in there; is there a more generic way to specify what we want? Going forward trusty isn't going to be it, and I don't want to push updates for something so trivial.