Replace distributed tracing testing application

[ricsanfre]

Issue description

For testing distributed tracing solution in picluster, linkerd's emojivoto application is used.

This application is not using OpenTelemetry, but Opentracing. Traces context propagation is not working anymore since NGINX ingress controller v1.10 has deprecated of OpenTracing. See #329.

A new testing application using OpenTelemtry is needed, so e2e traces context propagation can be tested.

Possible Alternatives

• Open Telemetry Demo application

[ricsanfre]

Is https://github.com/esigo/nginx-example a feasible option?