DNS: do not query CNAME if A succeeded already

[georglauterbach]

Fixes: #48048

Summary

When an A query succeeds, querying for CNAME again is

1. useless at best, and
2. creating unnecessary log entries in the DNS server.

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)

[georglauterbach]

Tests are failing:

I hope that is fixed with e3d7d84; I am not a PHP programmer, though; hence, I am not sure whether assertNotContains is used correctly here.

[solracsf]

Another failure:

There was 1 failure:

1) lib\Http\Client\DnsPinMiddlewareTest::testIgnoreSubdomainForSoaQuery
Failed asserting that an array does not contain 'subsubdomain.subdomain.example.com134217728'.

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[georglauterbach]

I'll be tackling this in two or three days.

[georglauterbach]

I updated the tests

[georglauterbach]

Checks are waiting for approval

[artonge]

Looks got besides the typo in the comment :)

[welcome]

Thanks for your first pull request and welcome to the community! Feel free to keep them coming! If you are looking for issues to tackle then have a look at this selection: https://github.com/nextcloud/server/issues?q=is%3Aopen+is%3Aissue+label%3A%22good+first+issue%22

[come-nc]

@georglauterbach Thanks a lot! This problem has been bothering people for a long time, I hope this will help reduce the chatter in the logs.

[come-nc]

/backport to stable30

[come-nc]

/backport to stable29

[come-nc]

/backport to stable28