Correct multiple traceparent header logging

[jtduffy]

Resolves #2126

Based on the logic in method and the associated comment, multiple TraceParent headers is only an issue if the headers differ. If all the headers are the same value, that's ok.

This moves the log statement and associated supportability metric to execute only if the headers are different values.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 70.75%. Comparing base (3b7d7d4) to head (ef213ce).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##               main    #2154   +/-   ##
=========================================
  Coverage     70.75%   70.75%           
- Complexity    10008    10010    +2     
=========================================
  Files           842      842           
  Lines         40346    40346           
  Branches       6115     6115           
=========================================
+ Hits          28546    28547    +1     
- Misses         9050     9051    +1     
+ Partials       2750     2748    -2     

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