Since we have the implementations of two types of replicated two-phase drops and unreplicated drop, dropCollection has different orders of cleanup operations depending on when we call UUIDCatalog::onDropCollection (by calling OpObserver::onDropCollection with CollectionDropType::kOnePhase ) and when we call _finishDropCollection.

This ticket is to unify all three implementations to always call _finishDropCollection before UUIDCatalog::onDropCollection.