Disallow in-place update of Port MAC address

While Neutron may technically allow updating the requested MAC address
of a port (for admin users only), in practice this only appears to work
when the port is not in use. Use Heat's replace-on-update flow, which is
designed to handle resources that are in use, to deal with changes to
the requested MAC.

Change-Id: I278584ecfe59a338d3135416527d9d3332808d2a
Depends-On: https://review.opendev.org/665692
Task: 31012

heat/engine/resources/openstack/neutron/port.py

@@ -245,7 +245,6 @@ class Port(neutron.NeutronResource):
             constraints=[
                 constraints.CustomConstraint('mac_addr')
             ],
-            update_allowed=True,
         ),
         ALLOWED_ADDRESS_PAIRS: properties.Schema(
             properties.Schema.LIST,
@@ -543,7 +542,6 @@ class Port(neutron.NeutronResource):
         result = super(Port, self).parse_live_resource_data(
             resource_properties, resource_data)
         result[self.QOS_POLICY] = resource_data.get('qos_policy_id')
-        result.pop(self.MAC_ADDRESS)
         fixed_ips = resource_data.get(self.FIXED_IPS) or []
         if fixed_ips:
             result.update({self.FIXED_IPS: []})

releasenotes/notes/port-mac-address-update-b377d23434e7b48a.yaml

@@ -0,0 +1,6 @@
+---
+fixes:
+  - |
+    ``OS::Neutron::Port`` resources will now be replaced when the
+    ``mac_address`` property is modified. Neutron is unable to update the MAC
+    address of a port once the port is in use.