Cors header should always be returned

[aledbf]

Which issue this PR fixes:

fixes #2138
fixes #2134

[k8s-reviewable]

This change is 

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: aledbf

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[codecov-io]

Codecov Report

Merging #2140 into master will decrease coverage by 0.14%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #2140      +/-   ##
==========================================
- Coverage   36.73%   36.59%   -0.15%     
==========================================
  Files          68       68              
  Lines        4837     4837              
==========================================
- Hits         1777     1770       -7     
- Misses       2793     2799       +6     
- Partials      267      268       +1

Impacted Files	Coverage Δ
cmd/nginx/main.go	27.21% <0%> (-4.44%)	⬇️

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