Title: #246: filter_users and filter_groups stop working properly in v 1.15
New patch set pushed and in the end the changes were not intrusive at all.
@pbrezina, I've partially taken your idea (with some changes).
Please, let me know if you're okay of the way the new plugin function has been
See the full comment at https://github.com/SSSD/sssd/pull/246#issuecomment-297186170