Implement a new IPA command allowing to retrieve the list of users matching the provided certificate. The command is using SSSD Dbus interface, thus including users from IPA domain and from trusted domains. This requires sssd-dbus package to be installed on IPA server. https://fedorahosted.org/freeipa/ticket/6646 Reviewed-By: David Kupka <dkupka@redhat.com> Reviewed-By: Jan Cholasta <jcholast@redhat.com>