writes /usbkey/config

def _write_config(config):
    '''
    writes /usbkey/config
    '''
    try:
        with salt.utils.atomicfile.atomic_open('/usbkey/config', 'w') as config_file:
            config_file.write("#\n# This file was generated by salt\n#\n")
            for prop in salt.utils.odict.OrderedDict(sorted(config.items())):
                if ' ' in six.text_type(config[prop]):
                    if not config[prop].startswith('"') or not config[prop].endswith('"'):
                        config[prop] = '"{0}"'.format(config[prop])
                config_file.write(
                    salt.utils.stringutils.to_str(
                        "{0}={1}\n".format(prop, config[prop])
                    )
                )
        log.debug('smartos.config - wrote /usbkey/config: %s', config)
    except IOError:
        return False

    return True