ldns: Ignore commented-out lines in resolv.conf.

This merges upstream PR 238 + an additional bug fix.

PR: 278721
Approved by: so
Security: FreeBSD-EN-24:11.ldns

(cherry picked from commit 3b092e4936c433889cc668ea9563c8fd437d1a3e)
(cherry picked from commit e95e16191f63240971687634a23c2defed64d713)