Refactor status update

[aledbf]

What this PR does / why we need it:

This PR extracts the leader election code from the status package to be able to use such a feature at the controller level for other operations.

Which issue this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close that issue when PR gets merged):

fixes #3565
fixes #2773

Special notes for your reviewer:

[aledbf]

/hold

[ElvinEfendi]

How is this fixing #2773? https://github.com/kubernetes/ingress-nginx/pull/3885/files#diff-cde3fffe2425ad7efaa8add1d05ae2c0R286 will only clean up hosts, but how are you making sure metric collector will not keep emitting ingress_controller_ssl_expire_time_seconds metrics when the pod it's not leader?

[aledbf]

How is this fixing #2773?

Last commit

[aledbf]

/hold

[codecov-io]

Codecov Report

Merging #3885 into master will decrease coverage by 0.72%.
The diff coverage is 17.64%.

@@            Coverage Diff             @@
##           master    #3885      +/-   ##
==========================================
- Coverage   55.05%   54.33%   -0.73%     
==========================================
  Files          82       83       +1     
  Lines        6121     6151      +30     
==========================================
- Hits         3370     3342      -28     
- Misses       2362     2427      +65     
+ Partials      389      382       -7

Impacted Files	Coverage Δ
internal/ingress/controller/status.go	0% <0%> (ø)
internal/ingress/controller/nginx.go	17.44% <0%> (-0.56%)	⬇️
internal/ingress/controller/controller.go	42.91% <0%> (-0.11%)	⬇️
internal/ingress/status/status.go	76.08% <100%> (+3.54%)	⬆️
internal/ingress/metric/collectors/controller.go	87.12% <56.25%> (-3.56%)	⬇️
internal/watch/file_watcher.go	80.76% <0%> (-3.85%)	⬇️

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[aledbf]

@ElvinEfendi ready for another review

[ElvinEfendi]

/lgtm

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: aledbf, ElvinEfendi

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[rajatjindal]

@aledbf - do you know why this code was removed. we are running into a regression where during rolling update the ingress status is getting removed by the last pod of old deployment and we are suspecting this is the issue here.

[aledbf]

@rajatjindal because we now use a callback https://github.com/kubernetes/ingress-nginx/pull/3885/files#diff-7d2578dc5d43f0b395d7cd3312c5c489R63

the ingress status is getting removed by the last pod of old deployment and we are suspecting this is the issue here.

This is expected. If you don't want this behavior you need to set UpdateStatusOnShutdown=false (flag --update-status-on-shutdown)