Why: Smoketests fail as they can not establish IPv6 connection to uvicorn
backend server.
https://github.com/vyos/vyos-1x/pull/2481 added a bunch of new smoketests.
While debugging those failing, it was uncovered, that uvicorn only listens on
IPv4 connections
vyos@vyos# netstat -tulnp | grep 8080
(Not all processes could be identified, non-owned process info
will not be shown, you would have to be root to see it all.)
tcp 0 0 127.0.0.1:8080 0.0.0.0:* LISTEN -
As the CLI already has an option to move the API communication from an IP to a
UNIX domain socket, the best idea is to make this the default way of
communication, as we never directly talk to the API server but rather use the
NGINX reverse proxy.
