Changes introduced by commit 6b8e4d6e69
were incomplete as not all time-sensitive checks were updated to match
revised "nta-lifetime" and "nta-recheck" values. Prevent rare false
positives by updating all NTA-related checks so that they work reliably
with "nta-lifetime 12s;" and "nta-recheck 9s;". Update comments as well
to prevent confusion.
(cherry picked from commit 9a36a1bba3)