contrib/rpm: require dbus-tools

The NM system unit uses dbus-send to tell NM to reload
configuration. We could replace dbus-send with 'kill -HUP', but the
systemd.service manual page warns against that because it is
asynchronous. So add the proper dependency.
17 jobs for bg/rpm-require-dbus-tools-rh1745659 in 86 minutes and 41 seconds (queued for 51 seconds)