[v2] pkg/vanflow/eventsource tests are flaky

[c-kruse]

Describe the bug
These unit tests are pretty fraught with timing sensitive assertions - the level they were written at counts on lots of asynchronous goings ons, and they were written such that I could sub in a real router container or a mock implementation.

For whatever reason I can run these tests in the most adverse conditions I can manage on my PC with count 500 and not come across these errors.

I plan to rewrite these in a less time-sensitive and async way.