Right now we clear the drop pending state after rollback to stable, and re-opening the catalog. During re-opening, we can register internal idents that need to be dropped. But if the internal ident is already registered, we'll hit a fatal assertion. So we need to flip the ordering.

What's worse, with the current ordering, is that catalog re-opening can register internal idents to drop, but we clear the state shortly after. These idents would not be dropped until a server restart.