Update condition for setting dd parent source

[hghotra]

What does this PR do?

This PR fixes a bug in Node Layer 26 which sets _dd.parent_source to xray for some edge cases which causes forwarder to ignore the traces. As a result, traces do not show up in Datadog.

Motivation

https://datadoghq.atlassian.net/browse/SLS-681

Testing Guidelines

• Ran integration tests
• Manually tested function

Additional Notes

Types of Changes

• Bug fix
• New feature
• Breaking change
• Misc (docs, refactoring, dependency upgrade, etc.)

Check all that apply

• This PR's description is comprehensive
• This PR contains breaking changes that are documented in the description
• This PR introduces new APIs or parameters that are documented and unlikely to change in the foreseeable future
• This PR impacts documentation, and it has been updated (or a ticket has been logged)
• This PR's changes are covered by the automated tests
• This PR collects user input/sensitive content into Datadog
• This PR passes the integration tests (ask a Datadog member to run the tests)

[codecov-commenter]

Codecov Report

Merging #95 into master will increase coverage by 0.13%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master      #95      +/-   ##
==========================================
+ Coverage   89.88%   90.01%   +0.13%     
==========================================
  Files          26       26              
  Lines         840      841       +1     
  Branches      141      142       +1     
==========================================
+ Hits          755      757       +2     
  Misses         55       55              
+ Partials       30       29       -1     

Impacted Files	Coverage Δ
src/trace/listener.ts	91.80% <100.00%> (+1.80%)	⬆️

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[Czechh]

Discussed with @hghotra - this LGTM.