Update cdh5-dev Dockerfile to reduce image size
Update cdh5-dev Dockerfile to reduce image size

In my testing with the factual/docker-cdh5-dev:latest image these
changes reduced the image size from 4.8GB to 2.87GB. This should help
with the issues we were seeing with the vfs storage driver.

- Combine instructions to reduce the number of layers and do some
cleanup in the layers
- Move around the build args and add some environment variables

bfs/docker-cdh5-dev