Calling the kodi-xxx target in ExecStart= was not actually the key to
fixing the shutdown bugs in 847b6ec65. 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-xxx in ExecStart= allows direction of kill signal to that
rather than to kodi-standalone wrapper. This allows the kill signal to hit
the indented executable. As well, using killall in the ExecStop= allows for
synchronous stopping and for kodi to do shutdown housekeeping tasks such as
saving settings, stopping services (web, zeroconf, etc.) and unloading things.