Fix tmpfs docker config

Merged username-removed-4080 requested to merge paulrbr/gitlab-runner:fix-tmpfs-docker-config into master

What does this MR do?

Fixes the issue #2701 (closed)

Are there points in the code the reviewer needs to double check?

Does this MR meet the acceptance criteria?

  • Tests
    • All builds are passing
    • Tested with a local build and worked as expected on services_tmpfs configuration
  • Branch has no merge conflicts with master (if you do - rebase it please)
Edited by username-removed-4080