controller: ignore non-service backends

[cpanato]

What this PR does / why we need it:

controller: ignore non-service backends

today the current behavior create an Invalid entry, using the proposed fix from Liggit it pushes it to the default backend, which makes sense to me

this is a bit unclear to me if that is ok. would like to get some feedback to learn more about this

/assign @rikatz

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 #7278

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.

[rikatz]

@cpanato probably lines 859, 1398 and 1614 can use this optimization and skip if this is backend.Service is nil, as we are not using it

[rikatz]

Personally I do not oppose myself of doing a redirect to the default backend if user creates an ingress pointing to a non service backend.

I just wanted the Ingress to give a feedback to the user of why that backend is being skipped, so if you can just add a log message would be great:

Suggested change

	if path.Backend.Service == nil {
	// skip non-service backends
	continue
	}
	if path.Backend.Service == nil {
	// skip non-service backends
	klog.V(3).Infof("Ingress %q and path %q does not contain a service backend, using default backend", ingKey, path.Path)
	continue
	}

[rikatz]

/lgtm
/approve
Thanks!!

[k8s-ci-robot]

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This pull-request has been approved by: cpanato, rikatz

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