fix: Avoid autostart service being executed twice

When ExecCondition returns an exit code that is non-zero but not 255,
the service is marked as "skipped" rather than "failed".
The skipped state may be treated as success by some versions of systemd,
thereby triggering OnSuccess!

Log: as title
Pms: BUG-343321

Author: yixinshark

systemd/dde-session-pre.target.wants/[email protected]

@@ -15,8 +15,8 @@ OnSuccess=dde-lock.service [email protected] dde-autostart
 Slice=session.slice
 Type=notify
 # only in quick login mode and x11
-ExecCondition=/bin/sh -c '[ "$DDE_QUICKLOGIN" = "true" ] || exit 2'
-ExecCondition=/bin/sh -c '[ "$XDG_SESSION_TYPE" = "%I" ] || exit 3'
+ExecCondition=/bin/sh -c '[ "$DDE_QUICKLOGIN" = "true" ] || exit 255'
+ExecCondition=/bin/sh -c '[ "$XDG_SESSION_TYPE" = "%I" ] || exit 255'
 ExecStart=/usr/bin/dde-quick-login
 SuccessExitStatus=0
 Restart=on-failure