gsutil needs access to the instance's metadata

Hi! We have faced with strange behaviour. gsutil needs to access to the instance's metadata, otherwise it's throwing exception:
`apitools.base.py.exceptions.ResourceUnavailableError: GCE credentials requested outside a GCE instance`

We do not want to provide access to metadata for everyone according to https://cloud.google.com/iam/docs/best-practices-for-securing-service-accounts#metadata-server-acccess

It reproduces only on GCP boxes. On AWS boxes works properly.

gsutil version: 4.65
5.3 - the same.

Start by reproducing the exception on a GCP box with gsutil 4.65 or 5.3, then trace how GCE credentials access the instance metadata. Compare this behavior with the working AWS-box case and verify that the resulting behavior does not require metadata access for everyone.

Written by the indexing model from the issue text.