x11-autostart: tweak for oem case

The nuance being that:
- alterator-setup package would change default.target
  for systemd providing a symlink of its own and making
  a backup of what was there (rc3 basically);
- 40-x11-autostart would ignore that backup;
- 99-oem-setup would do nothing about it all either;
- alterator-setup removal would restore rc3 symlink.

It's not pretty either, something more robust should be
invented some day.

features.in/x11-autostart/rootfs/image-scripts.d/40-x11-autostart

@@ -13,6 +13,7 @@ if [ -f "$INITTAB" ]; then
 fi
 
 ## ...and systemd, if any
-rm -f /etc/systemd/system/default.target
+## NB: alterator-setup's backup file can present a nice catch if left around
+rm -f /etc/systemd/system/default.target{,.bak}
 
 :