Incorrect added arguments if it`s an array. Raise exception about array

[imilyukov]

When input option with mode multiple, then raise next warning:
Warning: escapeshellarg() expects parameter 1 to be string, array given

Needed just test for type array of $arg and implode into string. But better use ArrayInput as wrapper, it`s accept an array and output prepared string by __toString() method.

See: https://github.com/schmittjoh/JMSJobQueueBundle/blob/master/Command/RunCommand.php#L360

Thanks ;)