usb-redir: An interface count of 0 is a valid value

An interface-count of 0 happens when a device is in unconfigured state when
it gets redirected. So we should not use 0 to detect not having received
interface info from our peer.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
