[2421] Add a testcase for empty zone too (which should throw EmptyZone)

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

@@ -21,7 +21,8 @@
                     "cache-enable": true,
                     "params": {
                         "example.org": "data/example.org",
-                        "example.com": "data/example.com-broken"
+                        "example.com": "data/example.com-broken",
+                        "example.net": "data/example.net-empty"
                     }
                 }
             ]

tests/lettuce/data/example.net-empty

@@ -0,0 +1 @@
+

tests/lettuce/features/auth_badzone.feature

@@ -35,3 +35,4 @@ 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