Properly notify a verification failure (should mark the downloaded blob as unusable)

Scenario: During a download, blob tag verification fails.

Expected Outcome: A helpful error message is logged and the whole download is retried (or scheduled to retry).

This should only happen a single time as false negatives on tag verification is less likely to occur than an attacker attempting to guess a correct tag for tampering. In an ideal world this should never happen, but a single retry can help making sure it's not a silly simple transfer/handling error.