fix(install): Increase stop timeout to 60 seconds (#731)

This is to ensure clean shutdown of Celery, with fully drained queues. This is needed as versions may change the event format and not be backwards compatible. FWIW this is a hacky workaround without a strong guarantee that the queues will be empty. Ideally we'd shutdown everything first, spin up the workers and check for queues being drained every second or so.