[uploader} Allows specifying mirror directories

[rmohr]

What this PR does / why we need it:

Make it possible to provide a sub-directory for the bucket where the dependencies should be uploaded to.

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:

Allow the uploader to put dependencies into a bucket subdirectory

[kubevirt-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: brianmcarey

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