This test initiates a 2-node RS and restarts the secondary as standalone, then immediately stops the primary. Since the validate_collections_on_shutdown.js override is active, the test tries to validate all the collections on the primary before stopping it. If, during this validation, the primary notices that the secondary is no longer a member, then it steps down and collection validation fails with "InterruptedDueToStepDown".

Pass skipValidation: true to ReplSetTest.stop() to avoid errors if the primary steps down before stopping.