allow weave-dns to bind to multiple addresses (ipv4 and ipv6)

[gucki]

I was talking to @rade on IRC. I use a custom docker network driver which connects containers to a custom bridge (not docker0) and assigns a routable address. To get weave-dns working I have to bind weave-dns to the routable address of the host, which is reachable by the container, and then pass --dns to the container. This works great so far.

However I can only specify one listen-address to weave-dns. So when I bind weave-dns to an ipv4 adress, the container has to have a routable ipv4 address. It's then not possible that have an ipv6-only container. It's the same the other way round: when I bind weave-dns to an ipv6 adress, the container has to have a routable ipv6 address. It's then not possible that have an ipv4-only container.

If weave-dns could be bound to an ipv4 and an ipv6 addres, this wouldn't be an issue anymore.

[vtolstov]

any news about ipv6 support for binding?

[awh]

@vtolstov as with #19, we have no plans to work on this at the moment.