Skip test_update_with_mac_address without admin credentials

Change-Id: I64e0075c4a518788451e4736768fcb49c5af40a0
diff --git a/functional/test_create_update_neutron_port.py b/functional/test_create_update_neutron_port.py
index 4e41b35..bd39bf4 100644
--- a/functional/test_create_update_neutron_port.py
+++ b/functional/test_create_update_neutron_port.py
@@ -78,6 +78,9 @@
         self.assertEqual(_mac, new_mac)
 
     def test_update_with_mac_address(self):
+        if not self.conf.admin_username or not self.conf.admin_password:
+            self.skipTest('No admin creds found, skipping')
+
         # Setup admin clients for updating mac_address
         self.setup_clients_for_admin()