Calling the kodi-gbm target in ExecStart= was not actually the key to
fixing the unclean shutdown bug. Adding the ExecStop= calling killall
to the exact target was needed.
This commit restores the call to kodi-standalone to allow the
"RestartApp" built in to work again and adds the key ExecStop= with
killall.
Direct call to kodi-gbm allows systemd to correctly assign the MAINPID to that
rather than to kodi-standalone wrapper. This change allows the kill signal to hit
the intended executable to enable a clean exit and internal updates to files on
exit such as ~/.kodi/userdata/settings.xml
Change can be propagated to other kodi packages after more extensive testing
