Adapt to the new behavior of disconnect in dbus-broker
    
    The dbus server was replaced in Fedora-29 to use dbus-broker.
    
    This server does not allow reconnects on a disconnect. certmonger
    was crashing as a result.
    
    The only way to directly pass a message between the dbus queue and
    the main tevent handle is via a signal. So when a disconnect is
    detected send a SIGTERM to getpid() in order to force a graceful
    shutdown.
    
    https://bugzilla.redhat.com/show_bug.cgi?id=1687698