test vlan: Fix race condition on MAC address

When creating VLAN without `address` property defined, systemd/udevd
will generate random MAC address and change it, hence we have race
problem during creation and query.

Fixed by explicitly set MAC address when creating VLAN in tests.

Signed-off-by: Gris Ge <cnfourt@gmail.com>

Author: cathay4t

src/ip/link/tests/vlan.rs

@@ -256,6 +256,8 @@ where
         "link",
         &parent_name,
         "name",
+        "address",
+        "0e:d1:49:08:27:84",
         vlan_name,
         "type",
         "vlan",