Constructing a Broadcaster already starts a watch which runs in the
background. Shutdown must be called to avoid leaking the goroutine. Providing
a context was supposed to remove the need to call Shutdown, but that did not
actually work because the logic for "must check for cancellation" was
accidentally inverted.
While at it, structured log output also gets tested together with checking for
goroutine leaks.
Kubernetes-commit: ff779f1cb56cf896405e52f7923188b99b88bb00