No Kafka logging after move to logstash-5.5.0

[trsmith2]

Initial output is:

~/dev/logstash-5.5.0$ bin/logstash -f config/logstash.conf
ERROR StatusLogger No log4j2 configuration file found. Using default configuration: logging only errors to the console.
Sending Logstash's logs to /home/trev/dev/logstash-5.5.0/logs which is now configured via log4j2.properties

And then no logging at all from Kafka client library.

Same behaviour in 5.1.7 and 6.2.1.

I've finally worked out a similar problem in older versions of Logstash (e.g. 5.3.1, 5.4.2) by rebuilding the gem with this commit included which pulls in an additional JAR that was previously required but missing - d8427e3.

This seems a like a new/different problem waiting for us when/if we move up to Logstash 5.5.0.

[tokred]

I guess this is related to #118. Probable fix #134 is still open though...