fix logstash gelf output severity level integer mapping
fix logstash gelf output severity level integer mapping

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