Introduced a proxy for the tenacity metrics stream

In a distributed environment the services may not be reachable from the public Internet. Given a scenario where the microservice dashboard is the only public available entry point, we must not call metrics/streams of the services directly from the javascript code. Instead we use this proxy method.

In our setup we needed this proxy method because
1. the microservice dashboard is running on https and the mixed http content was blocked
2. the microservice dashboard is running on the only public available machine. Direct calls to the services from the browser ends in a 404.