KCM: Idle-terminate the responder if the secrets back end is used
Existing with memory database would be fatal as we keep the ccaches in
memory then, but if the ccaches are stored in sssd-secrets, we can just
exit on idle.
Reviewed-by: Michal Židek <mzidek@redhat.com>
Reviewed-by: Simo Sorce <simo@redhat.com>