Replace grep calls with awk scripts to more precisely detect presence of
CDS and CDNSKEY records in a signed zone file, in order to prevent rare
false positives for the "smartsign" system test triggered by the strings
"CDS" and/or "CDNSKEY" being accidentally present in the Base64 form of
DNSSEC-related data in the zone file being checked.
(cherry picked from commit d0a73c7da6)