reduce debugging from info to debug in KafkaCheckpointManager.java

Author: Boris Shkolnik

samza-kafka/src/main/scala/org/apache/samza/checkpoint/kafka/KafkaCheckpointManager.scala

@@ -103,7 +103,7 @@ class KafkaCheckpointManager(
 
         systemProducer.send(taskName.getTaskName, envelope)
         systemProducer.flush(taskName.getTaskName) // make sure it is written
-        info("Completed writing checkpoint=%s into %s topic for system %s." format(checkpoint, checkpointTopic, systemName) )
+        debug("Completed writing checkpoint=%s into %s topic for system %s." format(checkpoint, checkpointTopic, systemName) )
         loop.done
       },