This avoids duplicating service call parsing in multiple places.
Further improvements to that code (like avoid using shell) can be
implemented in one place.
This process should be started from user session (most likely
qubes-session). New processes (of that user) will be created as
children of that session making logind and such crap happy. This should
also solve problems with EOF transmission (no additional "su" process)
and prevent loading all the environment multiple times.
