system: Add "netdev" group.

* gnu/system/shadow.scm (%base-groups): Add "netdev".

gnu/system/shadow.scm

@@ -89,6 +89,7 @@ (define %base-groups
         (user-group (name "kmem"))
         (user-group (name "video"))
         (user-group (name "audio"))
+        (user-group (name "netdev"))              ; used in avahi-dbus.conf
         (user-group (name "lp"))
         (user-group (name "disk"))
         (user-group (name "floppy"))