dnsdist-1.8.x: Undo an accidentally change of disableZeroScope to disableZeroScoping

[rgacogne]

Short description

Backport of #12738 to rel/dnsdist-1.8.x

'disableZeroScope' was accidentally changed to 'disableZeroScoping' in commit 597a91a

(cherry picked from commit d85c923)

Checklist

I have:

• read the CONTRIBUTING.md document
• compiled this code
• tested this code
• included documentation (including possible behaviour changes)
• documented the code
• added or modified regression test(s)
• added or modified unit test(s)
• checked that this code was merged to master