interface: fix MAC address learning issue

Fixed incorrect initialization of the `Interface` struct, which
caused learned MAC addresses to be ignored. The issue only affected
new interfaces, MAC address updates for existing interfaces were
handled correctly.

Signed-off-by: Renato Westphal <renato@opensourcerouting.org>

holo-interface/src/interface.rs

@@ -219,7 +219,7 @@ impl Interfaces {
                     flags,
                     addresses: Default::default(),
                     owner: Owner::SYSTEM,
-                    mac_address: Default::default(),
+                    mac_address,
                 };
 
                 // Notify protocol instances about the interface update.