[pve-devel] usb2 as default + tablet hotplug on config update

[Alexandre Derumier]

I have tested snapshot rollback with vmstate with usb1 controller
to new config with usb2 controller, It's works perfectly.
Tested with : debian squeeze, win2003, win2008R2.

Migration from qemu 1.3 to qemu 1.4, with the controller update, works fine too.