Docker install script fails to install docker registry

The tools/docker/install_docker.sh script fails during the
installation/setup of the docker registry.
The problem is that the used environment variables are wrong.

REGISTRY_IMAGE > DOCKER_REGISTRY_IMAGE
REGISTRY_IMAGE_NAME > DOCKER_REGISTRY_IMAGE_NAME

Change-Id: I16f051abe5c426f295c69d518b49c1b9a7b4cc94
Merge "Docker install script fails to install docker registry"