BSE: ignore warnings for remotely disconnected signals that are already disconnected
BSE: ignore warnings for remotely disconnected signals that are already disconnected

One possible scenario the old behavior could trigger bogus warnings is if
BSE still keeps track of closure and tries to disconnect after they have been
auto-disconnected by g_object_run_dispose.

GNOME/beast,GNOME/beast,GNOME/beast,tim-janik/beast,swesterfeld/beast,swesterfeld/beast,GNOME/beast,tim-janik/beast,tim-janik/beast,swesterfeld/beast,GNOME/beast,tim-janik/beast,GNOME/beast,swesterfeld/beast,swesterfeld/beast,swesterfeld/beast,swesterfeld/beast,tim-janik/beast,tim-janik/beast,GNOME/beast,tim-janik/beast