[Release 1.26] Add an integration test for flannel-backend=none

[manuelbuil]

Backport: #9582

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 14.85%. Comparing base (c7e6922) to head (d114693).

Additional details and impacted files

@@              Coverage Diff              @@
##           release-1.26    #9610   +/-   ##
=============================================
  Coverage         14.85%   14.85%           
=============================================
  Files               115      115           
  Lines              8475     8475           
=============================================
  Hits               1259     1259           
  Misses             6966     6966           
  Partials            250      250           

Flag	Coverage Δ
unittests	14.85% <ø> (ø)

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