Splintered traces in video-bench with multi-threading

[shyamjesal]

Describe the bug
Splintered traces in video-bench with multi-threading

Expected behavior
All the spans should have a common trace ID.

Logs

Notes
Tried multi-processing too (like this. This fixes the issue in docker compose, but when using knative, the traces get splintered.

[ustiugov]

Update: the issue seems to root in the fact that we do not pass the context when invoking many functions at once. It is not very clear how to do that in Python.