Incorrect non-ASCII characters in serial numbers fetched with libusb

Instead of getting the correct serial number it was prepended with
U+033A (COMBINING INVERTED BRIDGE BELOW). That character did not seem to be present when the serial is set up in the qdbd-init.sh script and
it is not read by HandshakeExecutor either.

There is a workaround of removing non-ASCII characters in place that should be removed once the true cause is identified and fixed.