fix: test has race condition on ws before connect with DX callbacks

[EnriqueL8]

Proposed changes

Fixes #1636 (comment)

h.Start() create the WS connection and in the before connect we added a callback handler DXConnect(). The test used to connect then add the handlers so sometimes the test might take longer so on reconnect the handler would be there but not the DXConnect mock.

Actually the test should add all the handlers before staring the FFDX plugin, this is the fix.

FYI @onelapahead

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Types of changes

• Bug fix
• New feature added
• Documentation Update

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• I have read the contributing guidelines.
• I have performed a self-review of my own code or work.
• I have commented my code, particularly in hard-to-understand areas.
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• I have added tests that prove my fix is effective or that my feature works.
• My changes have sufficient code coverage (unit, integration, e2e tests).

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.95%. Comparing base (1856c5c) to head (4edf8cd).
Report is 3 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1658   +/-   ##
=======================================
  Coverage   99.95%   99.95%           
=======================================
  Files         339      339           
  Lines       29780    29780           
=======================================
  Hits        29768    29768           
  Misses          8        8           
  Partials        4        4           

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