When openCollection is called without a timestamp, the regular catalogId mapping may be stale if there is a concurrent DDL commit in progress, such as a collection rename.

We can instead use the pending namespace map and extract the catalogId from the collection instance that we are in progress of committing. 

If the pending namespace is a drop and we don't have a collection to get the catalogId from we can fallback to use the regular mapping. If we find an entry using it we know that our snapshot cannot see the drop.