Fix replayer sigv4 logic without payload

[AndreKurait]

Description

Fixed a bug that was in the replayer on sigv4 requests without payloads when content-type did not exist. Cleaned up the unit tests for this

• Category: Bug fix
• Why these changes are required? sigv4 failures without payloads
• What is the old behavior before changes and new behavior after changes? sigv4 failures without payloads

Issues Resolved

Is this a backport? If so, please add backport PR # and/or commits #

Testing

Added unit tests

Check List

• [x] New functionality includes testing
  • [x] All tests pass, including unit test, integration test and doctest
• [x] New functionality has been documented
• [x] Commits are signed per the DCO using --signoff

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