Skip S3 check on S3 migrator command

[gamebits]

The attachments-switch-local-images-urls-to-s3-urls scans post_content for references to locally hosted media. If it finds media that is also hosted in Amazon S3, it updates the post content to point to S3.

The command should probably skip that check and just update the domain regardless. A site that is using S3 is not hosting media locally, so leaving the domain unchanged still results in a broken link, whether or not the file is in S3. We want to be able to add the file to S3 later without going back and running the command again.