[2421] Add a lettuce testcase where the zone file doesn't exist

tests/lettuce/configurations/auth/auth_badzone.config.orig

@@ -22,7 +22,8 @@
                     "params": {
                         "example.org": "data/example.org",
                         "example.com": "data/example.com-broken",
-                        "example.net": "data/example.net-empty"
+                        "example.net": "data/example.net-empty",
+                        "example.info": "data/example.info-doesnt-exist"
                     }
                 }
             ]

tests/lettuce/features/auth_badzone.feature

@@ -36,3 +36,4 @@ Feature: Authoritative DNS server with a bad zone
 
         A query for www.example.com should have rcode REFUSED
         A query for www.example.net should have rcode REFUSED
+        A query for www.example.info should have rcode REFUSED