[LI-HOTFIX] Log partition reassignment requests (#392)

TICKET = N/A
LI_DESCRIPTION =
Currently, there are no logs to show the partition reassignment requests sent via
the AlterPartitionReassignments request.
This PR adds the log to make troubleshooting easier
EXIT_CRITERIA = N/A

core/src/main/scala/kafka/controller/KafkaController.scala

@@ -2252,6 +2252,7 @@ class KafkaController(val config: KafkaConfig,
     if (!isActive) {
       callback(Right(new ApiError(Errors.NOT_CONTROLLER)))
     } else {
+      info(s"Processing API partition reassignments $reassignments")
       val reassignmentResults = mutable.Map.empty[TopicPartition, ApiError]
       val partitionsToReassign = mutable.Map.empty[TopicPartition, ReplicaAssignment]