'Get the value for the volume option.'

def _get_vol_option(self, volume_name, option_name):

    value = None
    options = self.zapi_client.get_volume_options(volume_name)
    for opt in options:
        if (opt.get_child_content('name') == option_name):
            value = opt.get_child_content('value')
            break
    return value
