fix(controller): Get the right resourceName for traefik.io.Fixes #3615

[BrunoTarijon]

When the var(apiGroupToResource) is executed and we set the traefik api to traefik.io, using the cli flag, the value is not yet setted with SetTraefikAPIGroup(). So the value for traefik.io is not in the map. I changed to a function that is only executed when it is called.

This try to fix the #3615 issue.

Checklist:

• Either (a) I've created an enhancement proposal and discussed it with the community, (b) this is a bug fix, or (c) this is a chore.
• The title of the PR is (a) conventional with a list of types and scopes found here, (b) states what changed, and (c) suffixes the related issues number. E.g. "fix(controller): Updates such and such. Fixes #1234".
• I've signed my commits with DCO
• I have written unit and/or e2e tests for my change. PRs without these are unlikely to be merged.
• My builds are green. Try syncing with master if they are not.
• My organization is added to USERS.md.

[sonarcloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud

[github-actions]

Published E2E Test Results

  4 files    4 suites   3h 24m 23s ⏱️
111 tests 103 ✅  6 💤 2 ❌
446 runs  420 ✅ 24 💤 2 ❌

For more details on these failures, see this check.

Results for commit dd369bc.

[github-actions]

Published Unit Test Results

2 174 tests   2 174 ✅  2m 54s ⏱️
  119 suites      0 💤
    1 files        0 ❌

Results for commit dd369bc.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 84.31%. Comparing base (6c873a9) to head (dd369bc).
Report is 69 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3759      +/-   ##
==========================================
+ Coverage   84.23%   84.31%   +0.08%     
==========================================
  Files         154      154              
  Lines       18021    18025       +4     
==========================================
+ Hits        15180    15198      +18     
+ Misses       1998     1991       -7     
+ Partials      843      836       -7     

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