[tests] skip running expected fail tests (#5038)

This commit skips running expected fail tests so that it will be easier
to find real failures and saves some time.

tests/scripts/thread-cert/test_service.py

@@ -49,6 +49,8 @@ SRV_1_SERVER_DATA = 'qux'
 
 
 class Test_Service(thread_cert.TestCase):
+    support_ncp = False
+
     topology = {
         LEADER: {
             'channel': 12,