Investigate replacing base image with CUDA image

[roclark]

Bobber currently uses a TensorFlow image from NGC as the base to use some of the TensorFlow functionality in the tests. While this is efficient, the Bobber image is quite large (12GB+ at present). By moving to a CUDA base image and installing TensorFlow inside the Bobber image, it might be possible to reduce the overall image size by several gigabytes with no change in functionality or performance. This will require a thorough investigation of the potential impacts of such a change.