SERVER-67678 introduced iet builder reset method, which is needed when adjusting hte bounds for wildcard index. However, completely resetting (clearing all the iets) is causing issues, as one reported in BF-25971. 

One would need to pop only those iets from the IetBuilder that are related to the corresponding wild-card index. One idea for that would be to keep track of this state, in order to know the count of the elements to pop