fix(controller): typo in catch-all CheckIngress error message

[aslafy-z]

What this PR does / why we need it:

Fixes a typo (spec.defaultBackend instead of spec.backend).

Types of changes

• [x] 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)
• [ ] Documentation only

Which issue/s this PR fixes

How Has This Been Tested?

This was not tested.

Checklist:

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

[k8s-ci-robot]

Hi @aslafy-z. Thanks for your PR.

I'm waiting for a kubernetes member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[strongjz]

/ok-to-test /priority backlog /triage accepted /kind bug

[rikatz]

/lgtm /approve Thanks

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: aslafy-z, rikatz

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