libusb seems to no allways call the completion callback for requests
canceled (which it is supposed to do according to the docs). So add
a limit to avoid qemu waiting forever.
Tested-by: BALATON Zoltan <balaton@eik.bme.hu>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Message-Id: <20200529072225.3195-1-kraxel@redhat.com>