[tests] update test_publish_meshcop_service.py (#7067)

- Relax the assumptions on the names of meshcop services so that it's
  OK for services to change names to resolve conflicts.
- Adjust timeouts.

tests/scripts/thread-cert/thread_cert.py

@@ -233,7 +233,7 @@ class TestCase(NcpSupportMixin, unittest.TestCase):
         # we have to add allowlist after nodes are all created
         for i, params in initial_topology.items():
             allowlist = params['allowlist']
-            if not allowlist:
+            if allowlist is None:
                 continue
 
             for j in allowlist: