[WIP] Add NVIDIA drivers for k8s linux agents

[wbuchwalter]

Automatically install NVIDIA drivers on linux agents for kubernetes.
Fixes #828

To Do:

• Add scripts to install NVIDIA drivers
• Ensure we are allowed to do this from a legal perspective
• Add unit tests
• Update GPU documentation

Implementation Details:

• There are two ways to install the NVIDIA drivers on Ubuntu:

  • By using the *.run file available on NVIDIA's website. This is the faster method, it takes ~2-3 minutes to install, but all the NVIDIA libraries are installed under /usr/lib/x86_64-linux-gnu/, which means mounting the drivers into the container can be painful and create some conflicts. A workaround is to map /usr/lib/x86_64-linux-gnu/ to a different directory in the container, but it can probably still create some issues if you need to add both /usr/lib/x86_64-linux-gnu/ and the mounted path to your LD_LIBRARY_PATH. Here is an example of a template.

  • By using apt with the ppa repository. Much slower to install, about ~12 minutes, so not ideal when scaling a lot, but the libraries are installed under a separate directory /usr/lib/nvidia-*. This allows us to mount only the drivers into the container and nothing else, which should prevent any dependency/versioning issue. Here is an example of a template. This is the way I used in this PR. I assume most people using GPUs will run jobs that are quite long (in ML we are typically talking about hours) so 12 minutes shouldn't be a big deal, and this should cause less issues.

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This change is 

[seanknox]

Thanks @wbuchwalter. Need to hold on this until we answer some legal questions about automatically installing.

[wbuchwalter]

I updated this PR to allow for different drivers installation scripts depending on the VMSize.
Currently only K80 and M60 VMs will have the drivers automatically installed.
P40 and P100 will need manual installation for now.
Also at some point there might be some customization needed for the NC24r and NV24r for infiniband.

[jackfrancis]

lgtm, thanks @wbuchwalter and @lachie83