Task context manager not properly clearing old task results

[bjester]

Observed behavior

The context manager for managing task progress along with a change event does not pass an existing task ID properly to a deletion query.

Expected behavior

The code should properly pass the existing task_id to the deletion query, instead of the queryset

User-facing consequences

Repeated channel publishing encounters this error.

Errors and logs

Steps to reproduce the issue

1. Create a channel
2. Add content
3. Publish the channel
4. Add more content
5. Try to publish again

Usage Details

• unstable branch