[Mimedefang] mimedefang muiltplexor leaves instances on stop

[Lucas Albers]

2.36 fixes the problem.
I hacked that same fix into 2.33.

> I'm curious what sort of init script other people are using;  I've been
> using one of the ones provided (not sure which one any more) since ~2.14
> or so, and I've *never* seen problems with slaves hanging around
> indefinitely after issuing a shutdown command.
>
> -kgd