Updating address pairs with xml doesn't work

Below command can't work because list element
"allowed_address_pairs" hasn't been updated
into the varaiable "attr.PLURALS"
"neutron port-update <port-uuid> \
--allowed-address-pairs list=true type=dict \
ip_address=10.0.0.1 --request-format xml"

Change-Id: I0d7dcca5f4848bc968f5c86fbeb46569c70c8fcd
Closes-Bug: #1229954

neutron/extensions/allowedaddresspairs.py

@@ -117,6 +117,8 @@ def get_updated(cls):
 
     def get_extended_resources(self, version):
         if version == "2.0":
+            attr.PLURALS.update({'allowed_address_pairs':
+                                 'allowed_address_pair'})
             return EXTENDED_ATTRIBUTES_2_0
         else:
             return {}

neutron/tests/unit/test_extension_allowedaddresspairs.py

@@ -99,10 +99,6 @@ def tearDown(self):
         super(AllowedAddressPairDBTestCase, self).tearDown()
 
 
-class AllowedAddressPairDBTestCaseXML(AllowedAddressPairDBTestCase):
-    fmt = 'xml'
-
-
 class TestAllowedAddressPairs(AllowedAddressPairDBTestCase):
 
     def test_create_port_allowed_address_pairs(self):
@@ -297,3 +293,7 @@ def test_create_port_remove_allowed_address_pairs(self):
             port = self.deserialize(self.fmt, req.get_response(self.api))
             self.assertEqual(port['port'][addr_pair.ADDRESS_PAIRS], [])
             self._delete('ports', port['port']['id'])
+
+
+class TestAllowedAddressPairsXML(TestAllowedAddressPairs):
+    fmt = 'xml'