instead of using 'replaceChild', simply set the appropriate
properties. When using the 'nodeUpdate' (protected function of extjs,
intended to be overwritten) instead of the private 'updateNode', it
will be called when the properties change
This way, the treenode stays the same and it can keep the selection
Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>