Fix duplicate fallback controllers from the controller chain

[saikishor]

Fixes: #3038

[Juliaj]

Fixes: #3038

Hi Sai, is there another issue that this PR fixes ? #3038 appears to be different from having duplicating fallback controllers. The scenario involves putting two (or more) controllers in the same chain group, each with a different fallback.

[codecov]

Codecov Report

❌ Patch coverage is 98.36066% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 89.31%. Comparing base (2794132) to head (cc69288).
⚠️ Report is 5 commits behind head on master.

Files with missing lines	Patch %	Lines
...ontroller_manager/test/test_controller_manager.cpp	98.33%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3108      +/-   ##
==========================================
+ Coverage   89.27%   89.31%   +0.04%     
==========================================
  Files         158      158              
  Lines       19299    19359      +60     
  Branches     1560     1560              
==========================================
+ Hits        17229    17291      +62     
+ Misses       1425     1423       -2     
  Partials      645      645              

Flag	Coverage Δ
unittests	89.31% <98.36%> (+0.04%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
controller_manager/src/controller_manager.cpp	77.04% <100.00%> (ø)
...ontroller_manager/test/test_controller_manager.cpp	95.85% <98.33%> (+0.10%)	⬆️

... and 2 files with indirect coverage changes

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[bmagyar]

thank you!