Enforce circuit breaker fallbacks with a talos law

[vaslabs]

• On a command failure execute fallback

it is essential to involve the system’s stakeholders when deciding how to handle calls made when the circuit is open."
Michael T. Nygard. Release It!: Design and Deploy Production-Ready Software (Pragmatic Programmers). Pragmatic Bookshelf, 2007.

• Fallbacks must be executed in a very short time - consider maximum timeout to be 100ms
  One of the reasons for failure is that systems may lack necessary resources to complete calls. By not constraining the fallback we are endangering the system in the same way of not having circuit breakers.