In s390x publish centos9 and kubevirtci jobs, do GCS calls without auth where possible

[chandramerla]

What this PR does / why we need it:
In s390x publish centos9 and kubevirtci jobs, do GCS calls to check for existence and contents of the publicly available files under kubevirt-prow/release/kubevirt/kubevirtci/ without authentication

As there are limits to number of refresh tokens that are issued per client-user combination in GCS, and beyond limits it may make old token to stop working, so we are reducing the token usage with this fix.
Ref: https://developers.google.com/identity/protocols/oauth2#5.-refresh-the-access-token,-if-necessary.
#3812

This PR is adds to the previous PR 3812 to fix the issue

This should address prow job failures like:
periodic-kubevirtci-bump-centos-base-s390x/1871405677058985984
publish-kubevirtci-s390x/1886882224930820096

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #

Special notes for your reviewer:
@brianmcarey As you suggested earlier, I'm using the curl without auth for publicly available URLs. Apologies for implementing it late. Please review.

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Release note:

NONE

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[chandramerla]

/cc @brianmcarey