Container fails to start if no inet6 family is available

[Artem Dvoretskiy]

It's a nginx configuration issue. Listening on ipv6 socket is hardcoded in config:

server {
        listen 80 default_server;
        listen [::]:80 default_server;
...

This leads to a fatal error if there's no ipv6:

nginx: [emerg] socket() [::]:80 failed (97: Address family not supported by protocol)

Should be configurable or may be use some kind of autodetection.