Only include dir_address if dirport != 0.
Only include dir_address if dirport != 0.

Onionoo's protocol specification says "Omitted if the relay does not
accept directory connections."  Let's do what the spec says.

fmapfmapfmap/onionoo-dev,fmapfmapfmap/onionoo-dev,fmapfmapfmap/onionoo-dev