Replace duplicated code snippet with calls to helper functions

Reduce code duplication by replacing a code snippet repeated throughout
system tests using "trusted-keys" and/or "managed-keys" configuration
sections with calls to keyfile_to_{managed,trusted}_keys() helper
functions.

bin/tests/system/synthfromdnssec/ns1/sign.sh

@@ -32,12 +32,4 @@ cat $infile $keyname.key > $zonefile
 $SIGNER -P -g -o $zone $zonefile > /dev/null
 
 # Configure the resolving server with a trusted key.
-cat $keyname.key | grep -v '^; ' | $PERL -n -e '
-local ($dn, $class, $type, $flags, $proto, $alg, @rest) = split;
-local $key = join("", @rest);
-print <<EOF
-trusted-keys {
-    "$dn" $flags $proto $alg "$key";
-};
-EOF
-' > trusted.conf
+keyfile_to_trusted_keys $keyname > trusted.conf