tests-extra: zone/notexists differentiates between unknown and unloadable

tests-extra/tests/zone/notexists/test.py

@@ -16,6 +16,10 @@ t.start()
 
 # Check if the server is answering and zone _isn't_ loaded
 resp = master.dig("notexist.", "SOA", udp=True)
+resp.check(rcode="SERVFAIL") # Unloadable zone, but in the zone database
+
+# Check if the server is answering and zone is unknown
+resp = master.dig("xfiles.", "SOA", udp=True)
 resp.check(rcode="REFUSED")
 
 # The other zone should answer without problem