Test-Proxy needs to reset the commit on git asset protection push failure

Not resetting the commit means that when users fix the recording and push again, the parent commit with the secret is _still present_ and git asset protection will prevent the `test-proxy push`.

Start at the test-proxy push flow and reproduce a git asset protection push failure using a recording that contains a secret. Trace what commit remains after the failure, then verify that retrying after fixing the recording no longer includes the parent commit with the secret.

Written by the indexing model from the issue text.