Fix nvidia-container-toolkit installation

[alberthli]

Corner case discovered: when a completely fresh computer runs our setup script, nvidia-container-toolkit cannot be installed because nvidia drivers haven't been installed yet. Two things to fix:

• use the command lspci | grep -i vga | grep -i nvidia | wc -l to check how many GPUs are physically available instead of an nvidia-smi command
• check if nvidia-smi can be run - if not, tell the user to install drivers and try to reinstall after (red text) and move on in the setup script