[TSK-Proxy] Re-connect to kafka when connection fails

[alistairking]

It seems that once librdkafka loses connections to all three brokers the proxy stops working even though it keeps running (I'm not sure why librdkafka does not reconnect automatically). We may want to figure out how to catch errors like the following and manually restart the kafka session.

%3|1530804633.556|ERROR|rdkafka#consumer-1| [thrd:loki.caida.org:9092/bootstrap]: loki.caida.org:9092/0: 1 request(s) timed out: disconnect (average rtt 133.878ms)
%3|1530804633.556|ERROR|rdkafka#consumer-1| [thrd:loki.caida.org:9092/bootstrap]: 3/3 brokers are down
%3|1530805233.692|FAIL|rdkafka#consumer-1| [thrd:penguin.caida.org:9092/bootstrap]: penguin.caida.org:9092/2: Receive failed: Disconnected
%3|1530805233.692|ERROR|rdkafka#consumer-1| [thrd:penguin.caida.org:9092/bootstrap]: penguin.caida.org:9092/2: Receive failed: Disconnected
%3|1530806132.762|FAIL|rdkafka#consumer-1| [thrd:riddler.caida.org:9092/bootstrap]: riddler.caida.org:9092/1: Receive failed: Disconnected
%3|1530806132.762|ERROR|rdkafka#consumer-1| [thrd:riddler.caida.org:9092/bootstrap]: riddler.caida.org:9092/1: Receive failed: Disconnected