Fix test_vlan.py (#2541)

[VS] Fix Vlan test for the signature of wait_for_n_keys

Author: lolyu

tests/dvslib/dvs_vlan.py

@@ -72,7 +72,7 @@ def get_and_verify_vlan_ids(self,
                                 polling_config=PollingConfig()):
         vlan_entries = self.asic_db.wait_for_n_keys("ASIC_STATE:SAI_OBJECT_TYPE_VLAN",
                                                     expected_num + 1,
-                                                    polling_config)
+                                                    polling_config=polling_config)
 
         return [v for v in vlan_entries if v != self.asic_db.default_vlan_id]
 
@@ -110,6 +110,6 @@ def verify_vlan_hostif(self, hostif_name, hostifs_oid, vlan_oid):
     def get_and_verify_vlan_hostif_ids(self, expected_num, polling_config=PollingConfig()):
         hostif_entries = self.asic_db.wait_for_n_keys("ASIC_STATE:SAI_OBJECT_TYPE_HOSTIF",
                                                       expected_num + 1,
-                                                      polling_config)
+                                                      polling_config=polling_config)
         return hostif_entries