Prevent delivery to close and back topic subs

Idea is as following.

1. Create two topic subscriptions.
2. publish 10,000 msgs. 
3. while messages are being received, close one subscription.
4. place the closed subscription again. Now as it is a new subscription, that should not get any messages.

This is implemented comparing timestamps of subscription and the message arrival. 
I would rather calll it Slot Delivery Worker ( -- reduces the changes of confusing people)