test: Test S3 backing store in E2E test

[adriankabala]

What issue type does this pull request address? (keep at least one, remove the others) /kind bugfix /kind enhancement /kind feature /kind documentation /kind test

What does this pull request do? Which issues does it resolve? (use resolves #<issue_number> if possible) References OPS-95

Please provide a short message that should be published in the vcluster release notes Fixed an issue where vcluster ...

What else do we need to know?

[cbron]

@adriankabala can you take a look into this soon or close, thx