Fix and test for LOGSTASH-559 authenticationType=>nil
Fix and test for LOGSTASH-559 authenticationType=>nil

joekiller/logstash-kafka,joekiller/logstash-kafka,Aloomaio/logstash-kafka,tinglinux/logstash-kafka,Aloomaio/logstash-kafka,tinglinux/logstash-kafka,opentable/logstash-kafka,opentable/logstash-kafka