[Backport 2.x] Ensure that challenge response contains body

[opensearch-trigger-bot]

Backport a528c91 from #4233.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 65.77%. Comparing base (2e9439d) to head (42aca48).

Additional details and impacted files

@@            Coverage Diff             @@
##              2.x    #4268      +/-   ##
==========================================
- Coverage   65.78%   65.77%   -0.02%     
==========================================
  Files         296      296              
  Lines       21258    21258              
  Branches     3471     3471              
==========================================
- Hits        13985    13982       -3     
- Misses       5530     5531       +1     
- Partials     1743     1745       +2     

Files	Coverage Δ
...ensearch/security/http/HTTPBasicAuthenticator.java	72.72% <100.00%> (ø)

... and 2 files with indirect coverage changes