Various fixes of mistakes in RPLs found using `rplint`

See individual commit messages for more information.

Note that "ENTRY has authority section with NS records, consider using MATCH subdomain" rule from rplint was turn off and its violations is left to investigate.

knot-resolver#386 (closed) should be probably fixed before merging this because iter_pcnamech.rpl and iter_pcnamechrec.rpl are now failing.