logind: when parsing a boolean via sd-bus the type must be "int"

And not bool.

src/login/logind-dbus.c

@@ -2293,7 +2293,7 @@ static int method_set_wall_message(
         int r;
         Manager *m = userdata;
         char *wall_message;
-        bool enable_wall_messages;
+        int enable_wall_messages;
 
         assert(message);
         assert(m);