Validate sticky sessions and worker balancing

[markstory]

Within the GCP sandbox, we need to validate that sticky sessions behave correctly. Once a pool of workers is running, we need to ensure that all brokers replicas get a roughly equivalent number of workers assigned.

When workers are restarted/deployed we should get roughly even distribution of workers to brokers. Furthermore, we shouldn't see failed task updates. With imbalanced workers we would see an increase in not found tasks when updating status.