Resolve "stale-serve and RPZ put in SERVFAIL cache unexpected record"

‼ NOTE: This was reverted in !7183 (merged) before the December 2022 release.

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In some serve stale scenarios, like when following an expired CNAME record, named could return SERVFAIL if the previous request wasn't successful.

Consider non-stale data when in serve-stale mode.

Closes #3678 (closed)