Stop using daemon mode in upstart scripts.

In daemon mode then upstart never detects if the container craps out / exits, and therefore never respawns correctly (at least in the upstart version in precise)..

I'd at least like to run containers not as a daemon - let me know if you feel strongly about this, as I'm happy to supply an alternate patch allowing both behaviors if there are cases where daemon mode is a good thing that I'm not seeing ;)