anchore plugin should show full tag regardless of whether gate_result has any rows

When gate_result has rows, we display the full tag, but when it’s empty we display the digest instead. It would be preferable to display the full tag in all cases.

The current behavior was a conscious decision made when the plugin was written, because the tag was not available unless there was a policy violation. Now the tag is available in eval output, so this change should be feasible.