Lua: Fix ExternalName services without endpoints.

[k8s-infra-cherrypick-robot]

This is an automated cherry-pick of #13154

/assign Gacko

[Gacko]

/retitle Lua: Fix ExternalName services without endpoints.
/triage accepted
/kind bug
/priority backlog
/lgtm

[Gacko]

/test pre-ingress-nginx-lua-test

[k8s-ci-robot]

@k8s-infra-cherrypick-robot: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
pre-ingress-nginx-lua-test	b17b868	link	true	/test pre-ingress-nginx-lua-test

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[Gacko]

I think the Lua test is failing because of a change in the E2E Test Runner image. The NGINX base image it was built on is not matching the one of the release-1.11 branch, as we removed Lua plugins at some point.

tl;dr: If the Lua test is the only thing not working, please see #13154 and #13429. There it worked.

[k8s-ci-robot]

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This pull-request has been approved by: Gacko, k8s-infra-cherrypick-robot

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