SERVER: Tone down shutdown messages for socket-activated responders
    
    When dealing with socket-activated responders, those may be shut
    themselves down after some inactivy period. And that's completely normal
    and expected, thus should not be logged as an fatal error.
    
    For the case when the responder is started by the monitor, however, it
    still makes sense to keep the code as it is as the responders won't shut
    themselves down in any normal scenario.
    
    Signed-off-by: Fabiano Fidêncio <fidencio@redhat.com>
    
    Reviewed-by: Jakub Hrozek <jhrozek@redhat.com>