Enable TLS for use in runners with Docker-in-Docker
Docker 19.03+ has automatic TLS generation enabled by default
This caused jobs to fail across our CE and EE pipelines, as well as for customers using our runners: https://gitlab.com/gitlab-org/gitlab-ce/issues/64959
Right now @craig is looking into applying a hotfix to the runners to disable automatic TLS generation, however in the interest of security it might be best if we look into actually enabling it properly. Or at least making an informed decision to leave it disabled.