Add org.opensuse.RebootMgr.service for DBus activation

[Vogtinator]

By using dbus activation, rebootmgrd is started on demand instead of causing

Error: The name org.opensuse.RebootMgr was not provided by any .service files

[Vogtinator]

Context: https://progress.opensuse.org/issues/151180

[lnussel]

Should be /bin/false so dbus-daemon itself does not activate the service. To enable autoactivation you can add the Alias=dbus-org.opensuse.RebootMgr.service to the [install] section of the service file. That way systemd takes care and would not be used of the service gets disabled.

[Vogtinator]

Hm, not sure whether that's enough. There's also the SystemdService property. The documentation says:

For bus-activatable services, do not include a [Install] section in the systemd service file, but use the SystemdService= option in the corresponding DBus service file

In any case, it still conflicts with the the current design philosophy as rebootmgrctl is-active is meant to tell whether rebootmgr is meant to be used...

[Vogtinator]

Hm, not sure whether that's enough. There's also the SystemdService property. The documentation says: ...

Actually, that would work. systemd/systemd#21520 only applies if the unit exists, so a missing unit should result in the proper ActivationFailed signal still, not a 30s timeout.