Disable cache for ubuntu cuda image building

- nvidia-docker mounts the host's driver libraries into the container
- when building an image on top of that, those libraries will get saved as empty into the next layer
  (they are usually overloaded by nvidia-docker runtime so it doesn't get noticed)
- when the host's gpu driver is updated, however, the old driver files remain and the new ones
  are mounted into the container -> driver libraries from multiple versions hanging around
  potentially causing issues. Don't allow it.