Transition from 0.0.0.0 listener to specific listener disallowed

Coderman reported back in August that if you try to change from a listener on 0.0.0.0 to a listener on a specific address, Tor will often fail, because it doesn't close the old listener until the new listener is open (in order to be undoable), but it can't open the new listener until the old one is closed.

See or-talk/or-dev thread, "Server node stalls on unsuccessful socks listener change."

It looks like we have two options:

1. Disallow the 0.0.0.0 -> non 0.0.0.0 change.
2. When transitioning from 0.0.0.0, accept that the transition will not be perfectly undoable.

[Automatically added by flyspray2trac: Operating System: All]