explicit set button focus respecting the 'dangerous' option

explicit set button focus respecting the 'dangerous' option

The line:
 > Ext.MessageBox.defaultButton = me.dangerous ? 2 : 1;
just set the button which should get triggered on an keyboard "Enter"
if no button is focused currently.

But often the 'Yes' buttons is focused so an enter press would
trigger it, even on a as 'dangerous' marked option.

Fix this, as else a to fast "Enter" press can cause more problems
than needed.

Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
Reviewed-By: Dominik Csapak <d.csapak@proxmox.com>