get rid of drax and fix device-control path
get rid of drax and fix device-control path

- drax is no longer build after garden removed support for btrfs
- path for device-control script is changed `./ci/scripts/device-control` => `./ci/helpers/device-control`

Signed-off-by: Charlie Vieth <ea3f0b85bda195c42ceb97da0f596f9d6d014e12@pivotal.io>

cloudfoundry-incubator/diego-release,cloudfoundry-incubator/diego-release,cloudfoundry-incubator/diego-release,cloudfoundry-incubator/diego-release