Comment 2 for bug 911385

The short version of this bug is that, if the database you're resuming from is in --ignore-databases, SchemaIterator will crash. Easy enough to avoid, but what should the behavior be here? In the branch currently linked to this bug, it does nothing: pt-table-checksum can't resume, so it just ends without doing any work. It would be ideal if we could warn, I think, but I doubt that'll be an easy change to make.