Reload, don't restart, dbus.service

Many bus clients get hopelessly confused when dbus-daemon is
restarted. So let's not do that.

Of course, this is not ideal either, because we end up stuck with a
possibly outdated dbus-daemon. But that issue will become irrelevant
in the glorious kdbus-based future.

Hopefully this also gets rid of systemd getting stuck after
dbus-daemon is restarted:

Apr 01 15:37:50 mandark systemd[1]: Failed to register match for Disconnected message: Connection timed out
Apr 01 15:37:50 mandark systemd[1]: Looping too fast. Throttling execution a little.
Apr 01 15:37:51 mandark systemd[1]: Looping too fast. Throttling execution a little.
...