nsec: correct wildcard proof check with queried for literal wildcard

The validation fails in current implementation when queried directly
for the wildcard. In that case the count of the common labels with the
NSEC record is the same, and not shorter by 1 (to accomodate wildcard
expansion).
18 jobs for validate-explicit-wildcard
in 8 minutes and 46 seconds and was queued for 8 seconds