Revert "vnc: set the right prefered encoding"

This patch was wrong, because the loop was already reversed,
so the first encoding was correctly set at the end of the loopp.

This reverts commit 14eb8b6829ad9dee7035de729e083844a425f274.

Signed-off-by: Corentin Chary <corentincj@iksaif.net>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
