[Modules] Fixes map-based backend concurrent adjust-with-init test

[yhassanzadeh13]

This PR resolves a concurrency issue in the map-based backend module's adjust-with-init test. The test's instability stemmed from the absence of defer in the waitgroup's Done method. Previously, the waitgroup was marked Done at the beginning rather than at the end of the goroutine, leading to an early evaluation of the cache's state.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (5ea8999) 55.57% compared to head (c6fc1d5) 55.62%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5275      +/-   ##
==========================================
+ Coverage   55.57%   55.62%   +0.04%     
==========================================
  Files        1003     1003              
  Lines       96785    96785              
==========================================
+ Hits        53791    53835      +44     
+ Misses      38919    38880      -39     
+ Partials     4075     4070       -5     

Flag	Coverage Δ
unittests	55.62% <ø> (+0.04%)	⬆️

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