Tweak to determination of fastest upstream

[DL6ER]

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Tweak logic so we can determine the fastest responding upstream server also in cases where sub-queries had to be asked because long-lived CNAMEs contained short-lived children. The current logic is currently broken when all-servers is used and queries where forwarded to more than one upstream server. In this case, Pi-hole always showed the last server which was got the query instead of the fastest responding one.

Fixes #1232

[DL6ER]

Has been confirmed working by original reporter in #1232

[pralor-bot]

This pull request has been mentioned on Pi-hole Userspace. There might be relevant details there:

https://discourse.pi-hole.net/t/pi-hole-ftl-v5-12-web-v5-9-and-core-v5-7-released/51795/1