Fix kicker launching
starting the desktop file from URL doesn't make too much sense as it
means we parse the mimeType beore then finding it's a desktop file.
Worse, this is broken where we only have a name, for example if you add
a KCM as a favourite.
It's done to avoid the blocking static methods, however there is an
alternate trick to save it blocking.
Reviewed-by: David Faure/Kai Uwe Broulik