SERVER-55581 made a change which returns a ScopedDbConnection created in getUnshardedCollInfo back to the connection pool when we are done with it. By returning this connection to the pool, we also implicitly reuse it the next time we try and establish a connection to the same host. In version 4.2, this causes a unit test to fail somewhat consistently (see BF-22220). After investigating this a short while, I believe that the issue is that the returned connection dies (for unknown reasons) and upon reuse, the logic we use to check the connection status returns a cached result, whereupon we try to reuse a broken connection and fail. In this ticket, investigate exactly what is going on, determine the best way to fix it, and do so.

Note that the changes in SERVER-55581 were reverted in both the 4.0 and 4.2 branches (but not 4.4, 5.0, or master) so any changes introduced here should also reintroduce the single-line change of SERVER-55581 (or equivalent) to 4.2 and 4.0.

This is a time-boxed 5-point tickets. Reassess with team after time-box to determine next steps.