kdig: compare wire format QNAMEs

This commit updates kdig's check_reply_question() function so that it
compares the original wire format QNAME of the query against the
original wire format QNAME of the response. Using knot_pkt_qname()
instead of knot_pkt_wire_qname() only compares the downcased QNAMEs.

RFC 5452:

    4.2.  Matching the Question Section

       DNS packets, both queries and responses, contain a question section.
       Incoming responses should be verified to have a question section that
       is equivalent to that of the outgoing query.

I think "equivalent" here means that the case of the QNAMEs should be
compared too.