[dock] Only enable GPU if available

Some execution environments may run CPU as well as GPU
code, this check for Nvidia driver presence will allow
to reuse the same environment on both.

It also updates the GPU option to use the latest version
provided by the nvidia-docker2 documentation.
6 jobs for only_enable_gpu_runtime_if_available in 42 minutes and 33 seconds (queued for 3 seconds)