request: add the native docker SSH support now available in v18.09

[diablodale]

Request to add support for Docker v18.09 native SSH.
This new connection method between client and engine allows for simple and shared SSH configuration which is far more common and more easily administered that the prior custom CA/certs solution.

Via the docker cli, it is easily done by setting the env var DOCKER_HOST=ssh://hostname or directly on the docker command using the -H parameter as in

docker -H ssh://hostname info

Here is the docker API code docker/cli#1014
and some articles on it
https://raesene.github.io/blog/2018/11/11/Docker-18-09-SSH/
https://medium.com/lucjuggery/docker-tips-access-the-docker-daemon-via-ssh-97cd6b44a53