resolved: correctly prove the non-existense of wildcard

resolved: correctly prove the non-existense of wildcard

* Current logic:
For each NSEC RR find the common suffix between the owner name and
the next name, append asterisk to that suffix and check that
generated wildcard is covered by the NSEC RR in question.

* New logic:
Find NSEC RR covering queried name, generate wildcard as
<asterisk>.<closest encloser> using this RR, then check if any
of the NSEC RRs covers generated wildcard.