DNS: NAPTR RR Replacement Length is incorrect

It seems the Replacement Length field calculated by Wireshark (which Wireshark calls "rReplacement Length"), is the length of the first label of the DNS name in the Replacement, instead of the entire DNS name length.

Issue found by Boaz

Bug:10700
Change-Id: I8b726f3a3bf316d688a40c3ade100d255ca3be42
Reviewed-on: https://code.wireshark.org/review/5300
Reviewed-by: Pascal Quantin <pascal.quantin@gmail.com>
(cherry picked from commit 3b8ed366ddd149f2cc1428a713235c18afc192e7)
Reviewed-on: https://code.wireshark.org/review/5329