Use trust anchors with 'dnssec-validation yes' in system tests

Explicitly use an empty 'trust-anchors' statement in the system
tests where it was used implicitly before.

In resolver/ns5/named.conf.in use the trust anchor in 'trusted.conf',
which was supposed to be used there.

bin/tests/system/database/ns1/named1.conf.in

@@ -35,6 +35,8 @@ options {
 	dnssec-validation yes;
 };
 
+trust-anchors { };
+
 zone "database" {
 	type primary;
 	database "_builtin empty localhost. hostmaster.isc.org.";

bin/tests/system/database/ns1/named2.conf.in

@@ -35,6 +35,8 @@ options {
 	dnssec-validation yes;
 };
 
+trust-anchors { };
+
 zone "database" {
 	type primary;
 	database "_builtin empty localhost. marka.isc.org.";