Make the cache-clearing-service deployable from CI
Make the cache-clearing-service deployable from CI

Currently, builds of the master branch are failing, as the
cache-clearing-service isn't an option in the Deploy App job. This
change should fix that.

alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet