Ability to quiet orchestrations

Sidekiq has the ability to quiet jobs (e.g. keep new jobs from be enqueued) enabling graceful shutdown. Because orchestrations contain jobs that are often coupled to each other code changes can be painful. If you have an orchestration like:
```
run JobB
run JobA
```
And move work from JobB to JobA when you deploy you might have JobB jobs already queued. When your updated code starts running the queued JobB jobs will run but you'll lose the work that you've moved to JobA. For these reasons a convenient tool would be the ability to stop starting new orchestrations. You can then wait for your running orchestrations to finish before making your code changes.