user/charge: implicitly exclude the NULL user from accounting
user/charge: implicitly exclude the NULL user from accounting

This is for now only useful to allow tests without accounting, but one could imagine
we would want to exclude some sockets from accounting alltogether. Such as the controller
socket.

Signed-off-by: Tom Gundersen <7c8224529a7c718e876cb2496c973509fde1e50e@jklm.no>

bus1/dbus-broker