Added configmap option to disable IPv6 in nginx DNS resolver

[kinghrothgar]

What this PR does / why we need it:
Adds an option to disable IPv6 of nginx dns reslover

Which issue this PR fixes: fixes #1986

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[k8s-reviewable]

This change is 

[aledbf]

@kinghrothgar apologies, please rebase and we are ready to go.

[aledbf]

@kinghrothgar please check the test failure (bad call to the buildResolvers function)

[aledbf]

@kinghrothgar you need to update this test

ingress-nginx/internal/ingress/controller/template/template_test.go

Line 355 in d1ae7ff

resolver := buildResolvers(ipList)

[kinghrothgar]

Pushed that fix a few hours ago, waiting for the CI to finish.

[aledbf]

@kinghrothgar please execute make code-generator and commit the changes

[coveralls]

Coverage increased (+0.06%) to 39.802% when pulling cb848d8 on kinghrothgar:master into ad2238c on kubernetes:master.

[kinghrothgar]

So the current CI fail seems to have nothing to do with code I touched or am I miss reading it?

[aledbf]

/approve

[aledbf]

@kinghrothgar thanks!

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

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

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