Rsync'd files are wiped on startup

[mfontanini]

This may be the behavior by design but I'm seeing that every time I restart the validator it erases all previously rsync'd files and re-downloads all of them. Since it takes a few minutes to download all of these files, this basically disallows validating ROAs until it comes back up.

Is there a way to disable this? I'd like to have the minimum possible downtime in between restarts.