There was quite a bit of drift between the main Dockerfile and this one since we last touched it. It’s heavier than it needs to be, but by using the main development image as the base here, we have less duplicated and outdated code overall.
instead of launching isolated tasks via `systemctl`, treat
`awx.main.isolated.run` as an executable that knows how to daemonize
additionally, add `setup.py isolated_build` for isolated Tower source
distribution