2970. [security] Adding a NO DATA negative cache entry failed to clear

any matching RRSIG records.  A subsequent lookup of
                        of NO DATA cache entry could trigger a INSIST when the
                        unexpected RRSIG was also returned with the NO DATA
                        cache entry.  [RT #22288]

bin/tests/system/resolver/ns6/example.net.db.in

@@ -0,0 +1,6 @@
+$TTL 600
+@	IN SOA	ns hostmaster 1 1800 900 604800 600
+@	IN NS	ns
+@	IN MX	0 mail
+ns	IN A	10.53.0.6
+mail	IN A	10.53.0.6