From a local PB, it seems the fcv_upgrade_downgrade... passthrough suites are taking a significant amount of time to complete. Looking at the JS hook, it seems we may be sleeping the thread for long durations while running the test, which will cause slowness. This is also run per test, which means that tests that previously took <1s to complete might take upwards of 20+s now.

We should reduce the amount of times we run setFCV and sleep per test, and we should also avoid running the hook on every test. In mongosync passthrough testing, we would execute the hook only once every n=15 or n=20 tests, which would lead to the same test coverage over time assuming randomness in test order.