ensure we use the right hostname when testing repo URLs

[evgeni]

Why are you introducing these changes? (Problem description, related links)

The application generates links and we should assert that the generated links are valid.
However, as the FQDN of the application might not be reachable from the place the tests run from, we used to override the "host" (netloc) part of the URL with the IP address we know from the SSH config.
That means that if the application generates a link with the wrong host, we don't notice it, as we override it.

Related:

• Container hostname change breaks unattended_url for external host registration #482
• configure hosts for ActionDispatch::HostAuthorization middleware #471

What are the changes introduced in this pull request?

• Instead of overriding the host in the URL, only override it at the connection level, ensuring the right hostname is tested in the URL.

How to test this pull request

Steps to reproduce:

• Tests should cover this

Checklist

• Tests added/updated (if applicable)
• Documentation updated (if applicable)