add hystrix circuit breaker

[poblin-orange]

Hystrix circuit breaker offers a good support in spring cloud, to manage backends timeout, avoid overflowing them in case of slow.
see

• https://github.com/Netflix/Hystrix/wiki/Configuration
• http://cloud.spring.io/spring-cloud-netflix/spring-cloud-netflix.html
  This instrumentation limits the concurrent iaas request (default is 10 concurrent cpi orders, will tune later).

[poblin-orange]

tip. the hystrix metrics can be streamed from http://core_user:core.password@director_ip:8080/admin/hystrix.steam from an external hystrix dashboard.
To deploy a hystrix dashboard on a cf deployment, see https://github.com/orange-cloudfoundry/cloudfoundry-operators-tools-boshrelease