Tracing: support jaeger-agent tracer

[cocotyty]

Title: One line description
When we used envoy and jaeger together, we found that envoy does not support sending data directly to jaeger-agent.
Description:

Describe the the desired behavior, what scenario it enables and how it
would be used.

[optional Relevant Links:]

Any extra documentation required to understand the issue.
https://github.com/jaegertracing/jaeger-client-cpp
https://www.jaegertracing.io/docs/1.22/architecture/

[suniltheta]

Could this issue be same as #16401 which is closed due to staleness. May be we should revisit this problem.

I also notice that if we are using latest image from https://hub.docker.com/r/jaegertracing/all-in-one then the zipkin traces sent to this jaeger collector doesn't show up on jaeger UI.

The last working version seem to be jaegertracing/all-in-one:1.21

Checking if jaegertracing/jaeger-operator#1441 is the root cause of the problem.

cc: @darox

[suniltheta]

So setting COLLECTOR_ZIPKIN_HOST_PORT instead of COLLECTOR_ZIPKIN_HTTP_PORT fixed the issue for me.
A deprecated variable COLLECTOR_ZIPKIN_HTTP_PORT was removed from v1.22
ref: https://github.com/jaegertracing/jaeger/releases/tag/v1.22.0

[suniltheta]

Hi @cocotyty is this still an issue?