`rake uploads:migrate_to_s3` needs some love

[pfaffman (Jay Pfaffman)]

@tgxworld

The code in the rake task is still valid from what I can tell. Did you run into any specific problems that made you bring up the issues above?

uh. Hmm. I’ll try again.

I think I’m confused because it seems like it should be able to read those variables from SiteSettings and I don’t understand how the backup and upload buckets get defined from just the S3 bucket.