Refactor ingress validation in webhook

[aledbf]

What this PR does / why we need it:

This fixes an issue with Kubernetes v1.18 where a default PathType is configured by default.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Which issue/s this PR fixes

fixes #5457

How Has This Been Tested?

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I've read the CONTRIBUTION guide
• I have added tests to cover my changes.
• All new and existing tests passed.

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: aledbf

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [aledbf]

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[codecov-io]

Codecov Report

Merging #5459 into master will decrease coverage by 0.26%.
The diff coverage is 55.91%.

@@            Coverage Diff             @@
##           master    #5459      +/-   ##
==========================================
- Coverage   58.64%   58.37%   -0.27%     
==========================================
  Files          88       88              
  Lines        6913     6946      +33     
==========================================
+ Hits         4054     4055       +1     
- Misses       2414     2445      +31     
- Partials      445      446       +1     

Impacted Files	Coverage Δ
cmd/nginx/main.go	5.98% <0.00%> (-0.43%)	⬇️
internal/ingress/controller/template/template.go	79.89% <0.00%> (-0.22%)	⬇️
internal/ingress/types.go	0.00% <ø> (ø)
internal/k8s/main.go	52.17% <0.00%> (-17.06%)	⬇️
internal/ingress/annotations/class/main.go	54.54% <50.00%> (-34.35%)	⬇️
internal/ingress/controller/controller.go	49.58% <83.33%> (+0.18%)	⬆️
internal/ingress/controller/store/store.go	59.78% <83.33%> (-0.30%)	⬇️
internal/admission/controller/main.go	90.47% <96.77%> (+4.36%)	⬆️
internal/admission/controller/server.go	100.00% <100.00%> (ø)

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[aledbf]

/retest