Our buildsystem/image (Yocto/OE) is using systemctl as default and we have defined 'systemctl' as
3rd parameter (e.g. see drivers/lcd4l.cpp), but users of our source could
use systems without 'systemctl' in their own buildsystems/images,
therefore it makes sense to have a fallback to 'service'.
This should avoid patching the sources.
Thx GetAway for hint.