libusb_get_bos_descriptor: Don't log an error on devices without a BOS

An error of LIBUSB_ERROR_PIPE simply means the device has no BOS, so don't
log an error to the console for this.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
linux_udev: Join the hotplug-event-thread when we stop event monitoring

To ensure that it is stopped before we continue (and if later libusb
gets re-initialized start another thread).

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