SERVER-51095 made PrimaryOnlyService::stepdown explicitly interrupt tracked OperationContexts, because a PrimaryOnlyService instance could create a new OperationContext in the window between when the stepdown thread kills OperationContexts and calls PrimaryOnlyService::stepdown via updateMemberState.

On shutdown:

First ReplicationCoordinator::stepdown is called.

Then ReplicationCoordinator::shutdown is called, which calls PrimaryOnlyService::shutdown, which joins all running instances.

Finally, all OperationContexts are marked as killed.

However, the first step ReplicationCoordinator::stepdown is allowed to fail. In that case, PrimaryOnlyService::shutdown may try to join a running instance whose OperationContext has not been interrupted.

To avoid this, PrimaryOnlyService::shutdown should also explicitly interrupt all its OperationContexts.