Whenever we transition out of PRIMARY, or into ROLLBACK or REMOVED, we call a function to close all connections. With SERVER-24574, however, that call now only closes non-internal connections, where it used to close all connections.
We should think about whether or not this is safe for transitions to ROLLBACK or REMOVED, and may want to just go ahead and close all (including internal) connections in those cases as it is much easier to reason about the system if you don't have to worry about time going backwards on a single connection.