spice_usb_device_manager_add_dev: check auto_ok before freeing libusb device list
spice_usb_device_manager_add_dev: check auto_ok before freeing libusb device list

In preparation for a different SpiceUsbDevice.

freedesktop-unofficial-mirror/spice__spice-gtk,freedesktop-unofficial-mirror/spice__spice-gtk,Fantu/spice-gtk,flexVDI/spice-gtk,freedesktop-unofficial-mirror/spice__spice-gtk,dezelin/spice-gtk,SPICE/spice-gtk,fgouget/spice-gtk,guodong/spice-gtk,elmarco/spice-gtk,elmarco/spice-gtk,guodong/spice-gtk,dezelin/spice-gtk,SPICE/spice-gtk,guodong/spice-gtk,mathslinux/spice-gtk,freedesktop-unofficial-mirror/spice__spice-gtk,Fantu/spice-gtk,mathslinux/spice-gtk,dezelin/spice-gtk,elmarco/spice-gtk,mathslinux/spice-gtk,SPICE/spice-gtk,dezelin/spice-gtk,mathslinux/spice-gtk,SPICE/spice-gtk,elmarco/spice-gtk,fgouget/spice-gtk,flexVDI/spice-gtk,fgouget/spice-gtk,Fantu/spice-gtk,guodong/spice-gtk,Fantu/spice-gtk