dracut/vmklive/display-manager-autologin.sh: fix autologin for sddm

if a non-default username is set, this won't work.
autologin for other DMs already use $USERNAME

dracut/vmklive/display-manager-autologin.sh

@@ -25,7 +25,7 @@ fi
 if [ -x ${NEWROOT}/usr/bin/sddm ]; then
     cat > ${NEWROOT}/etc/sddm.conf <<_EOF
 [Autologin]
-User=anon
+User=${USERNAME}
 Session=plasma.desktop
 _EOF
 fi