further tidying of primary/secondary terminology in system tests

this changes most visble uses of master/slave terminology in tests.sh
and most uses of 'type master' or 'type slave' in named.conf files.
files in the checkconf test were not updated in order to confirm that
the old syntax still works. rpzrecurse was also left mostly unchanged
to avoid interference with DNSRPS.

bin/tests/system/limits/ns1/named.conf.in

@@ -23,11 +23,11 @@ options {
 };
 
 zone "." {
-	type master;
+	type primary;
 	file "root.db";
 };
 
 zone "example" {
-	type master;
+	type primary;
 	file "example.db";
 };