HalfOpen state implementation in CircuitBreaker

Hi all,

I would like to propose to implement the half open state as described in
this diagram:

http://martinfowler.com/bliki/images/circuitBreaker/state.png.

When the halfOpenAfter timeout is reached, the circuitBreaker change into a
HALF_OPEN state. If the next exchange is successful, the CircuitBreaker
opens, otherwise it returns to the OPEN state again.

I created a CAMEL issue on jira and attached a possible implementation:

https://issues.apache.org/jira/browse/CAMEL-8039