Don't run revert scripts when rolling back under --log-only.

Had an issue where we deployed with `--log-only`, a verify script had a bug
that caused it to fail, and then the changes were reverted! Completely
unacceptable.

So now, verify scripts still run under `--log-only` (unless they are not
enabled or `--no-verify` is passed), but revert scripts never run.
Resolves #112.