Avoid unnecessary downloads in audit.

[reitermarkus]

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Since curl_check_http_content was fixed, when auditing the mactex cask, it will first try to download a ~4GB file since it comes from a http:// URL. Only then will it check the https:// URL.

The audit currently fails since the download exceeds the 600 seconds timeout of the audit.

This fixes the function to first check if the https:// URL is reachable and only then download the http:// URL as well. Otherwise, only the reachability of the http:// URL is checked.

[BrewTestBot]

Review period skipped due to critical label.