nixos/smartd: Refactor to use config.networking.fqdnOrHostName

nixos/modules/services/monitoring/smartd.nix

···
 
 let
 
-  host = config.networking.hostName or "unknown"
-       + optionalString (config.networking.domain != null) ".${config.networking.domain}";
+  host = config.networking.fqdnOrHostName;
 
   cfg = config.services.smartd;
   opt = options.services.smartd;