CI Runner failures using `docker:dind`

https://github.com/docker-library/docker/issues/175 introduced a change that will break customer configurations explicitly using the DOCKER_HOST variable.

More details in gitlab-org/gitlab-runner#4566 (closed)

Workaround

If you are experiencing this error you have the following workaround option

gitlab-org/gitlab-runner#4566 (comment 199290492)

For now please either remove DOCKER_HOST variable or set explicitly the 19.03.0-dind/18.09.7-dind image version.