[stable-only][OVN] Set VETH interface MAC address before up

Set the VETH interface MAC address of the metadata namespace before
setting this interface as up.

This change was introduced in [1] and should be backported to stable
versions.

[1]https://review.opendev.org/c/openstack/neutron/+/894026/12/neutron/agent/ovn/metadata/agent.py#710

Closes-Bug: #2055561
Change-Id: Ied8f7a5b6c0e9c295e8e040546c53bd98206ef12
(cherry picked from commit ac63999)

Author: ralonsoh

neutron/agent/ovn/metadata/agent.py

@@ -586,13 +586,13 @@ def provision_datapath(self, datapath):
             ip1, ip2 = ip_lib.IPWrapper().add_veth(
                 veth_name[0], veth_name[1], namespace)
 
+        # Configure the MAC address.
+        ip2.link.set_address(metadata_port_info.mac)
+
         # Make sure both ends of the VETH are up
         ip1.link.set_up()
         ip2.link.set_up()
 
-        # Configure the MAC address.
-        ip2.link.set_address(metadata_port_info.mac)
-
         cidrs_to_add, cidrs_to_delete = self._process_cidrs(
             {dev['cidr'] for dev in ip2.addr.list()},
             datapath_ports_ips,