Update doc to use RabbitMQ 4.1

Author: seunghun1ee

doc/source/operations/upgrading-openstack.rst

@@ -35,10 +35,10 @@ Notable changes in the |current_release| Release
 There are many changes in the OpenStack |current_release| release described in
 the release notes for each project. Here are some notable ones.
 
-RabbitMQ 4.0
+RabbitMQ 4.1
 ------------
 
-RabbitMQ is being upgraded to 4.0 in Epoxy. Existing transient queues must be
+RabbitMQ is being upgraded to 4.1 in Epoxy. Existing transient queues must be
 migrated on Caracal prior to upgrading.
 
 .. warning::
@@ -69,6 +69,12 @@ Then execute the migration script:
 
    $KAYOBE_CONFIG_PATH/../../tools/rabbitmq-queue-migration.sh
 
+After queue migration is finished, upgrade RabbitMQ to 4.1 by running followin command
+
+.. code-block:: bash
+
+   kayobe kolla ansible run rabbitmq-upgrade 4.1
+
 stackhpc.linux collection
 -------------------------