Update upstart_service to support start/stop on

It used to be that the upstart_service was being picky about start_on
and stop_on. Make this simpler as some of the neutron services need
explicit ordering. Also support pidfiles.

Reorder site.yml neutron data plane roles.
Merge pull request #537 from blueboxgroup/startstop-refactor

Update upstart_service to support start/stop on