Avoid random websocket test failures by waiting for http server to start

[samanhappy]

There were some random test failures for TestWSPing, as shown here.

These failures should emerged when the test cases began running before the http server was ready.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (707e216) 99.08% compared to head (06a0397) 98.78%.
Report is 1 commits behind head on main.

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Additional details and impacted files

@@            Coverage Diff             @@
##             main     #474      +/-   ##
==========================================
- Coverage   99.08%   98.78%   -0.31%     
==========================================
  Files          82       85       +3     
  Lines        5820     5863      +43     
==========================================
+ Hits         5767     5792      +25     
- Misses         40       52      +12     
- Partials       13       19       +6     

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