Change the AutoGetCollectionForRead class to no longer take collection MODE_IS locks, when flagged to do so, while still performing the same checks and providing the same read semantics.
The flagging may be done through a special enum constant to be passed to the constructor, or similar approach. The idea is that we can change individual call sites to use lock-free reads or not.
This ticket probably can only be tested through a unit test or dbtest until at least
SERVER-50145 is done.