bug(bootloader-driver): unicode error in _data_as_list function

[cfobel]

The following code (see here):

    if isinstance(data, np.ndarray):
        data = data.tostring()
    if isinstance(data, six.string_types):
        data = list(bytes(data.encode('utf8')))
    return data

needs to be replaced with:

    if isinstance(data, np.ndarray):
        data = data.tobytes()
    if isinstance(data, six.string_types):
        data = list(bytes(data))
    return data