Previously, if they changed in torrc during a SIGHUP, all was well,
since we would just clear all transient entries from the addrmap
thanks to bug 1345.  But if you changed them from the controller, Tor
would leave old mappings in place.

The VirtualAddrNetwork bug has been here since 0.1.1.19-rc; the
AutomapHosts* bug has been here since 0.2.0.1-alpha.