Bill Nottingham authored May 10, 2011 and Dan Williams committed May 10, 2011

1) Don't require NM, but run after it. This allows this service
to be installed without bringing up NetworkManager. Add -x so that
it exits if NM isn't running.

2) Install as a want of network.target, instead of multi-user.target.
This allows us to skip it if nothing requires network.target or the
legacy $network SysV capability.