Fix xauth annoying error

```
 DAEMON: Adding new display : 0  on vt 7 ...
 DAEMON: Adding cookie to "/run/sddm//A:0-ziZKlQ"
/usr/bin/xauth:  file /run/sddm//A:0-ziZKlQ does not exist
 DAEMON: Display server starting..
```

This should fix this annoying error finally....

Just need to touch the file first..

PS: Why QFile::remove()??