We cache things like validators and 'capped' status on the Collection object so we do not need to go all the way to storage and open up a storage transaction every time we want to check the value.

As far as I know, 'temp' cannot change with 'collMod', but it can with 'renameCollection', and on rollback.

This is needed for SERVER-38139 to ban temporary collections in transactions without having to consult the storage engine an extra time for every transaction statement.