Parses the result for a wpa command over an interface.

@private
@static
@category wpa_cli
@param {function} callback The callback function.
function parse_command_interface(callback) {
    return function(error, stdout, stderr) {
        if (error) {
            callback(error);
        } else {
            var output = parse_command_block(stdout.trim());
            if (output.result === 'FAIL') {
                callback(new Error(output.result));
            } else {
                callback(error, parse_command_block(stdout.trim()));
            }
        }
    };
}