Cos instances need a service account to install gpu drivers

[militarpancho]

It's a question more than a bug, but, I'm having trouble when installing cos-extension gpu in the last version of cos (cos-89 stable), so...The logs are below:

I0825 16:07:31.625556    1007 main.go:21] Checking if this is the only cos_gpu_installer that is running.
I0825 16:07:31.626389    1007 install.go:74] Running on COS build id 16108.403.51
I0825 16:07:31.626404    1007 installer.go:187] Getting the default GPU driver version
I0825 16:07:31.626491    1007 utils.go:72] Downloading gpu_default_version from https://storage.googleapis.com/cos-tools/16108.403.51/gpu_default_version
E0825 16:07:31.769160    1007 artifacts.go:106] Failed to download gpu_default_version from public GCS: failed to download gpu_default_version, status: 401 Unauthorized
E0825 16:07:31.770506    1007 install.go:175] failed to get default driver version: failed to get default GPU driver version: failed to download artifact gpu_default_version: failed to download gpu_default_version

Diving in this problem, I realized that when download a file from "https://storage.googleapis.com..." the installer always add an "Authorization" header and cause the request to a public bucket to fail. It seems like a service account is needed in the instance and added in this header, but actually i don't need any service account user in my gcp instances. So I think this is limiting the installation of gpu drivers. Any chance you or I can change the code to only require service account authentication when needed, because gpu_default_version is a public file. Thanks in advance!