In quiesce_mode.js, when we wait for the pauseWhileKillingOperationsAtShutdown here and here, we assume that the waitForFailPoint command will be killed by the server, since the server has started killing new operations and marked all existing operations as killed. However, if the waitForFailPoint command was an existing operation, then even though it was marked as killed, it might not have any remaining interrupt points and could complete successfully.