Enable Listening to IPv6

[DZ945brH]

If you are running containers on an IPv6 enabled host and are supplying IPv6 addresses to containers, connecting to the container is failing via IPv6.
If I am connecting to the host->container remotely, docker-proxy prefers connecting via IPv6 and also fails. Enabling nginx to listen to IPv6 as well as legacy IP addresses fixes this:

Before patch:

root@XXX:~/hiccup# telnet 172.17.2.2 80
Trying 172.17.2.2...
Connected to 172.17.2.2.
Escape character is '^]'.
^CConnection closed by foreign host.

root@XXX:~/hiccup# telnet 2001:678:XXX::2 80
Trying 2001:678:XXX::2...
telnet: Unable to connect to remote host: Connection refused

After patch:

root@XXX:~/hiccup# telnet 172.17.2.2 80
Trying 172.17.2.2...
Connected to 172.17.2.2.
Escape character is '^]'.
^CConnection closed by foreign host.

root@XXX:~/hiccup# telnet 2001:678:XXX::2 80
Trying 2001:678:XXX::2...
Connected to 2001:678:XXX::2.
Escape character is '^]'.
^CConnection closed by foreign host.