Fix synthesis race condition

[jveski]

Fixes two race conditions: one in the test and one in the code.

The main race condition is reached when a composition has been created but not yet synthesized. It will be eligible for rollout, even though that doesn't make sense. We will always reach it on the next pass of the loop anyway.

The test race condition is simpler. It occurs because we use two separate test compositions in the test, and Kubernetes doesn't provide synchronization across resources. The same race isn't an issue in production because we don't care so much about ordering in within the eventually consistent system.

[jveski]

I'm going to merge this myself because all of the reviewers are out for the holidays. I will continue to leave a coherent PR trail for upcoming changes and we will review retroactively.