Hi,
this patch partially solves the ticket
https://fedorahosted.org/sssd/ticket/2590
It does not subscribe to the systemd dbus interface and does only
the polling (this would have to be done anyway for the case
the interface is not available).
I will investigate how to add the systemd/dbus check as well,
but the attached patch should decrease priority of the ticket.
Thanks,
Michal