Add tracing metrics to oxd server

How to enable tracing metrics in oxd server

1. Download and run jaeger locally or server from : https://www.jaegertracing.io/download/. Jaeger can be run locally/server directly using Docker:

   docker run -d -p 5775:5775/udp -p 16686:16686 jaegertracing/all-in-one:latest

2. In oxd-server.yml set following properties for tracing.

   **enable_tracing** - set this property to "true" to enable tracing.
   
   **tracer** - mention tracer whether "jaeger" or "zipkin".
   
   **tracer_host** - mention tracer host
   
   **tracer_port** - mention tracer port
   

3. Start OXD server. Now server can be monitored at jaeger on url : http://{jaeger-host}:16686