rauc.service.in: ensure systemd will terminate RAUC before D-Bus
rauc.service.in: ensure systemd will terminate RAUC before D-Bus

If we do not specify After=dbus.service, RAUC can be shut down by
systemd after D-Bus is killed. This will trigger the r_on_name_lost()
handler and let RAUC terminate with an error message and failure exit code:

| rauc[197]: Connection to the bus can't be made for de.pengutronix.rauc
| systemd[1]: Stopping D-Bus System Message Bus...
| systemd[1]: Stopping Rauc Update Service...
| [...]
| systemd[1]: rauc.service: Main process exited, code=exited, status=1/FAILURE
| systemd[1]: rauc.service: Failed with result 'exit-code'.

Signed-off-by: Enrico Joerns <a2e5f936c390f36494e46e71bcfbe365bb1e8c49@pengutronix.de>

rauc/rauc,jluebbe/rauc,jluebbe/rauc,rauc/rauc,jluebbe/rauc,ejoerns/rauc,ejoerns/rauc,rauc/rauc,ejoerns/rauc