(PUP-876) Enable upstart service provider on Redhat

This commit allows the upstart service provider to function on Redhat
systems. Redhat 6 included support for upstart and while it wasn't
widely embraced it is available for use.

The 'serial' and 'tty' services on Redhat 6 systems have instances which
the service type/provider cannot handle, so we have to ignore them for
the upstart provider to work out of the box.