Change a normal behaviour being logged from warning to info.
Change a normal behaviour being logged from warning to info.

As we added lot of kafkaConsumers, people are begining to see the
warning logs that are added by the driver when connexion are closed
by the broker.

But this is the normal behaviour, so we remove it from being a
"warning" as it usually make clients worry needlesly.

criteo/kafka-sharp,criteo/kafka-sharp