Use rndc_dumpdb() in the "dnssec" system test

(cherry picked from commit 44c0cc88)

bin/tests/system/dnssec/clean.sh

@@ -92,7 +92,7 @@ rm -f ./ns3/ttlpatch.example.db ./ns3/ttlpatch.example.db.signed
 rm -f ./ns3/ttlpatch.example.db.patched
 rm -f ./ns3/unsecure.example.db ./ns3/bogus.example.db ./ns3/keyless.example.db
 rm -f ./ns4/managed-keys.bind*
-rm -f ./ns4/named_dump.db
+rm -f ./ns4/named_dump.db*
 rm -f ./ns6/optout-tld.db
 rm -f ./ns7/multiple.example.bk ./ns7/nsec3.example.bk ./ns7/optout.example.bk
 rm -f ./ns7/split-rrsig.db ./ns7/split-rrsig.db.unsplit

bin/tests/system/dnssec/tests.sh

@@ -3098,9 +3098,8 @@ status=$((status+ret))
 
 echo_i "check that key id are logged when dumping the cache ($n)"
 ret=0
-rndccmd 10.53.0.4 dumpdb 2>&1 | sed 's/^/ns4 /' | cat_i
-sleep 1
-grep "; key id = " ns4/named_dump.db > /dev/null || ret=1
+rndc_dumpdb ns4
+grep "; key id = " ns4/named_dump.db.test$n > /dev/null || ret=1
 n=$((n+1))
 test "$ret" -eq 0 || echo_i "failed"
 status=$((status+ret))