The docker-in-docker image now enables TLS by default (added in
docker-library/docker#166), which complicates testing in our
environment, and isn't needed for the tests we're running.
This patch sets the `DOCKER_TLS_CERTDIR` to an empty value to
disable TLS.
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
(cherry picked from commit b1a3c1aad1)
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>