The rollback fuzzer suites utilize the RollbackTestFixture to run randomized rollback testing. Some of the suites (e.g. rollback_fuzzer_clean_shutdowns) will shut down nodes at random times. After we shutdown a node, we wait until there is a stable primary so that we can continue doing writes in the test. The way we check this can be racy, though, if we get a current primary that then steps down, and we get that same node as a secondary. Instead of asserting that the primary and secondary are not equal, I think it would be simpler to just check if we shut down the original primary. If so, then we need to wait for a new primary. Otherwise, we shouldn't need to wait, since the original primary should be stable, since it is supported by an arbiter.