KafkaSession: clarify use of ContextClassLoader

Change-Id: If2ac679c0efae80aa1cb13d32a4d6d0d3b4a55ce
diff --git a/src/main/java/com/googlesource/gerrit/plugins/kafka/session/KafkaSession.java b/src/main/java/com/googlesource/gerrit/plugins/kafka/session/KafkaSession.java
index ae8aa2b..fcb5263 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/kafka/session/KafkaSession.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/kafka/session/KafkaSession.java
@@ -47,6 +47,10 @@
     }
 
     LOGGER.info("Connect to {}...", properties.getProperty("bootstrap.servers"));
+    /* Need to make sure that the thread of the running connection uses
+     * the correct class loader otherwize you can endup with hard to debug
+     * ClassNotFoundExceptions
+     */
     setConnectionClassLoader();
     producer = new KafkaProducer<>(properties);
     LOGGER.info("Connection established.");