- Received a report that when cert-manager is selected to
  manage all certificates that gitlab-runner nodes do not
  work due to a template issue. Could not replicate this
  issue locally for testing.
- Verified behavior in template that creates a mount for
  custom-ca-certificates when it should not be there. Added
  a guard to prevent this behavior.
- Initial reporter states this patch resolved issue with
  certmanager and gitlab-runner nodes.

Resolves #806

Signed-off-by: Robert Marshall <rmarshall@gitlab.com>