Please bump Docker machine to newer version

Could you please bump docker-machine to a newer version:

https://github.com/docker/machine/releases

There were some problems fixed in newer versions that would help me a lot.

https://gitlab.com/gitlab-org/gitlab-ci-multi-runner/blob/9-4-stable/dockerfiles/ubuntu/Dockerfile#L20

Must bump for people using gitlan-runner behind proxies :/

mentioned in merge request !640 (merged)

changed milestone to %9.5

closed via merge request !640 (merged)