Add KError = 9

According official page, 9 is unused:
http://search.cpan.org/~sgladkov/Kafka/lib/Kafka.pm

But I met lots of "Unknown error, how did this happen? Error code = 9"
So I Found out:
http://search.cpan.org/~sgladkov/Kafka/lib/Kafka.pm

I think the official page is not up to date.