In this commit, we fix a bug that would cause resolution of items in
/etc/hosts (or the like) to fail as Tor wouldn't recognize them as
proper host names. With this commit, we'll catch this error and fall
back to the system's resolver.
With this commit, if --tor.active is specified, then IPv6 addresses
will no longer go through the connmgr.TorLookupIP function from btcd.
This function does not have proper IPv6 support and would fail with
the error "tor general error". Instead, use the system resolver.
TCP addresses resolved through net.ResolveTCPAddr give a default network
of "tcp", so we'll map back the correct network for the given address.
This ensures that we can listen on the correct interface (IPv4 vs IPv6).
