Upstart configuration clean-up

Clean up Upstart configuration so that:

1) Fork is correctly accepted (and thus the PID can be properly tracked).
2) collectd is actually stopped on 'stop' (it doesn't with the old configuration).
3) File looks more like what's in /etc/init/ on a default Ubuntu install.
usage is only if you have something special going with the job, like a DB name: http://upstart.ubuntu.com/cookbook/#usage