Fix return value of empty-MAC guard in metadata agent

The empty-MAC guard in _get_port_ip4_ips_and_ip6_flag returns []
instead of the expected (list, bool) tuple. This would cause a
crash if a port with an empty MAC column were encountered during
datapath provisioning. Fix the return value to ([], False).

Conflicts:
  neutron/agent/ovn/metadata/agent.py

Closes-Bug: #2150543

Assisted-By: Claude Opus 4.6
Change-Id: Idc7d789ffe0289bf28fb289456196c307dd4a706
Signed-off-by: Eduardo Olivares <eolivare@redhat.com>
(cherry picked from commit 6f529d9)
(cherry picked from commit bd4fa33)

Author: eduolivares

neutron/agent/ovn/metadata/agent.py

@@ -639,7 +639,7 @@ def _get_port_ip4_ips_and_ip6_flag(self, port):
         if not port.mac:
             LOG.warning("Port %s MAC column is empty, cannot retrieve IP "
                         "addresses", port.uuid)
-            return []
+            return [], False
         mac_field_attrs = port.mac[0].split()
         ips = mac_field_attrs[1:]
         if not ips:

neutron/tests/unit/agent/ovn/metadata/test_agent.py

@@ -481,6 +481,15 @@ def test__get_provision_params_returns_provision_parameters_ipv6(self):
         self._test__get_provision_params_returns_provision_parameters(
             'fe80::f816:3eff:feb6:c0c0')
 
+    def test__get_port_ip4_ips_and_ip6_flag_empty_mac(self):
+        """Should return empty IPs for ports with empty MAC column."""
+        port = mock.Mock()
+        port.mac = []
+        port.uuid = 'fake-uuid'
+        ip4_ips, any_ip6 = self.agent._get_port_ip4_ips_and_ip6_flag(port)
+        self.assertEqual([], ip4_ips)
+        self.assertFalse(any_ip6)
+
     def _test_provision_datapath(self, ipv6_enabled):
         """Test datapath provisioning.