Bug#911107: deluged sends port=0 via IPv6 announce instead of the correct port

[Tiger!P]

Originally I reported this on the deluged package, but I think it is in
libtorrent.
I think this has also been reported [1] to the upstream of libtorrent

[1] https://github.com/arvidn/libtorrent/issues/3306

Tiger!P