Entity submission backlog: apply create as update

[ktuite]

This other issue #682 captured the main cases of force-applying submissions held in the backlog. An update could be applied without the right base version, and an update about a non-existent entity that appeared to be created offline could be applied as a create.

These didn't cover the case where a missing offline create comes in after an update was force-applied as a create. In this case, we need to apply the create as an update.