aws-xray-propagator: ensure trace state is not overwritten

[majanjua-amzn]

Description

The problem: Currently, the AWS X-Ray propagator overrides the trace state when returning the context by providing the default trace.TraceState() instead of attempting to retrieve this information from the provided context.

The solution: Check for a valid trace state in the provided context and propagate it to the new context if it exists.

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration

• Unit tests

Does This PR Require a Core Repo Change?

• No.

Checklist:

See contributing.md for styleguide, changelog guidelines, and more.

• Followed the style guidelines of this project
• Changelogs have been updated
• Unit tests have been added
• Documentation has been updated: N/A

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: majanjua-amzn / name: Mahad Janjua (dfb5e15)

[jj22ee]

Instead of letting this code trigger AttributeError, can you check if trace.get_current_span(context=context) and trace.get_current_span(context=context).get_span_context() and trace.get_current_span(context=context).get_span_context().trace_state are not none to set trace_state?

[jj22ee]

        tracestate = trace.TraceState()
        if context is None:
            context = Context()
        else:
            # put your logic here to update `trace_state` if it exists in `context`

Suggestion if you want to avoid the possibility of extracting trace_state from a new Context() when "context is None".