Avoid dns rebinding checks when the domain is whitelisted

What does this MR do?

In this MR we use the current domain whitelist that can be configured in the Admin area, to avoid blocking the URL because of the dns rebinding checks, when the domain is whitelisted.

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/66950

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Does this MR meet the acceptance criteria?

Conformity

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