Comment 3 for bug 373539

I don't think this is a duplicate.

Robert has indicated that there are times when the obsolete packs shouldn't be removed as part of pack.

Having a `bzr pack --delete-obsolete-packs` that doesn't actually pack seems wrong to me.

Having a command that explicitly removes old "stuff" seems more intuitive. It is more than just obsolete_packs, but the upload directory too.