When knxd crashes during physical address programming, devices do not work at all anymore

[dallmair]

With knxd 0.14.56.2, it happened several times now (at least to one of our users, but also to @Doumanix) that physical device address programming crashed knxd. At the very minimum, that is a bug in knxd.

However, when this happens it also has the effect that the programmed Selfbus device gets completely stuck. In this state, one can still toggle the programming LED by pressing the programming button, but that's it. No bus communication at all, nothing, until the device is restarted (disconnect from and reconnect to bus). We should be more benign in this situation.