explicitly set v4 and v6 listen ports

Signed-off-by: Adrian Nöthlich <git@promasu.tech>

Author: promasu

docker/nginx.conf

@@ -27,7 +27,8 @@ http {
     include             mime.types;
     access_log          /dev/stdout;
     error_log           /dev/stderr;
-    listen              [::]:8080 ipv6only=off;
+    listen              8080;
+    listen              [::]:8080;
     proxy_redirect      off;
     proxy_set_header    Host                $host;
     proxy_set_header    X-Real-IP           $remote_addr;