setting myfamily on a bridge should warn (and fail?)

Per http://archives.seul.org/tor/talk/Nov-2011/msg00209.html we should do something to inform the user of his mistake if he sets myfamily on a bridge.

I'd argue for 'and fail' too, except presumably the real problem is that the user set myfamily on his public relay, and that's what ought to fail -- but it's harder for the public relay to realize this.