bundles/systemd-networkd: add dummy interfaces

bundles/systemd-networkd/files/template-dummy.netdev

@@ -0,0 +1,3 @@
+[NetDev]
+Name=${name}
+Kind=dummy

bundles/systemd-networkd/items.py

@@ -63,6 +63,21 @@ for interface, config in node.metadata['interfaces'].items():
             },
         }
         weight = 61
+    elif interface.startswith('dummy'):
+        files[f'/etc/systemd/network/60-iface-{interface}.netdev'] = {
+            'source': 'template-dummy.netdev',
+            'content_type': 'mako',
+            'context': {
+                'name': interface,
+            },
+            'needed_by': {
+                'svc_systemd:systemd-networkd',
+            },
+            'triggers': {
+                'svc_systemd:systemd-networkd:restart',
+            },
+        }
+        weight = 61
     else:
         weight = 50