Fix informers on stale object deletion [1.9 backport]

[mariomac]

Backport of PR #1420

[codecov]

Codecov Report

Attention: Patch coverage is 57.57576% with 42 lines in your changes missing coverage. Please review.

Project coverage is 80.95%. Comparing base (fb6dbef) to head (0b4a918).
Report is 1 commits behind head on release-1.9.

Files with missing lines	Patch %	Lines
pkg/kubecache/meta/informers_init.go	57.57%	39 Missing and 3 partials ⚠️

Additional details and impacted files

@@               Coverage Diff               @@
##           release-1.9    #1424      +/-   ##
===============================================
- Coverage        81.13%   80.95%   -0.18%     
===============================================
  Files              146      146              
  Lines            14731    14772      +41     
===============================================
+ Hits             11952    11959       +7     
- Misses            2199     2231      +32     
- Partials           580      582       +2     

Flag	Coverage Δ
integration-test	58.50% <0.00%> (-0.23%)	⬇️
k8s-integration-test	59.92% <57.57%> (-0.21%)	⬇️
oats-test	34.00% <0.00%> (-0.10%)	⬇️
unittests	51.74% <26.26%> (-0.15%)	⬇️

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[grcevski]

LGTM!