Add option to override server provider default DNS nameservers

[firyx]

PULL REQUEST

Overview

Novogara server provider is using local DNS caching resolver unbound. It seems it is not configured correctly and doesn't resolve some domains, e.g. sia-storage.net.

This PR removes usage of unbound and uses custom defined nameservers set via ansible-private variable.

Example for Visual Changes

Checklist

Review and complete the checklist to ensure that the PR is complete before assigned to an approver.

• All new methods or updated methods have clear docstrings
• Testing added or updated for new methods
• Verify if any changes impact the WebPortal Health Checks
• Approriate documentation updated
• Changelog file created

Issues Closed

[linear]

SKY-451 Fix Novogara dnslink issues

[kwypchlo]

This PR removes usage of unbound and uses custom defined nameservers set via ansible-private variable.

I don't think I like this solution, using unbound has its merits and we're removing it even if it's the default that came with debian distro. We should figure out what was wrong and fix that instead of dropping the cache layer completely and adding complexity for portal operators - how would a portal operator even decide which server he needs to overwrite the nameservers on, there's not immediate error or anything happening, the only way we figured out that the dns was not resolving was a user reporting the issue.