[DHCP agent] Fetch OVN Metadata port from plugin

OVN metadata port from NetworkCache is being used and fixed_ips
for it were not available at the time network was added into
the cache. So let's re fetch it if it is available in the cache.

Related-Bug: #1982569
Related-Bug: https://bugzilla.redhat.com/show_bug.cgi?id=2213862
Change-Id: Ie0ec43566fa2b3e13b4917493336ce1519c9b6bb
(cherry picked from commit 0afa24d9af)

neutron/agent/linux/dhcp.py

@@ -1136,7 +1136,8 @@ class Dnsmasq(DhcpLocalProcess):
         m_ports = [port for port in self.network.ports if
                    self._is_ovn_metadata_port(port, self.network.id)]
         if m_ports:
-            for fixed_ip in m_ports[0].fixed_ips:
+            port = self.device_manager.plugin.get_dhcp_port(m_ports[0].id)
+            for fixed_ip in port.fixed_ips:
                 if fixed_ip.subnet_id == subnet.id:
                     return fixed_ip.ip_address
 

neutron/tests/unit/agent/linux/test_dhcp.py

@@ -3125,6 +3125,8 @@ class TestDnsmasq(TestBase):
     def test__generate_opts_per_subnet_with_metadata_port(self):
         config = {'enable_isolated_metadata': False,
                   'force_metadata': False}
+        self.mock_mgr.return_value.plugin.get_dhcp_port.return_value = \
+            FakeOvnMetadataPort()
         self._test__generate_opts_per_subnet_helper(config, True,
             network_class=FakeNetworkDhcpandOvnMetadataPort)