Document scale-down with hostnames

Starting in Train, we'll allow operators to scale down with hostnames
instead of instance IDs.

Change-Id: I9b1bd34a150b0d1e9e54243232c94cd9283d218d
Depends-On: I23fc92dfdb1808dec59f0ff7f96910ab8b5ccf45

deploy-guide/source/features/deployed_server.rst

@@ -721,6 +721,17 @@ user are as follows:
 
 Scaling Down
 ^^^^^^^^^^^^
+
+.. admonition:: Train
+   :class: train
+
+   Starting in Train and onward, `openstack overcloud node delete` can take
+   a list of server hostnames instead of instance ids. However they can't be
+   mixed while running the command. Example: if you use hostnames, it would
+   have to be for all the nodes to delete.
+
+The following instructions are only useful when the cloud is deployed on Stein
+or backward.
 When scaling down the Overcloud, follow the scale down instructions as normal
 as shown in :doc:`../post_deployment/delete_nodes`, however use the following
 command to get the uuid values to pass to `openstack overcloud node delete`

deploy-guide/source/post_deployment/delete_nodes.rst

@@ -5,7 +5,7 @@ Deleting Overcloud Nodes
 
 You can delete specific nodes from an overcloud with command::
 
-    openstack overcloud node delete --stack $STACK_NAME --templates [templates dir] <list of nova instance IDs>
+    openstack overcloud node delete --stack $STACK_NAME --templates [templates dir] <list of nova instance IDs or hostnames starting in Train>
 
 This command updates the heat stack with updated numbers and list of resource
 IDs (which represent nodes) to be deleted.
@@ -17,6 +17,14 @@ IDs (which represent nodes) to be deleted.
    prevent accidental node removal.
    To skip it, please use "--yes".
 
+.. admonition:: Train
+   :class: train
+
+   Starting in Train and onward, `openstack overcloud node delete` can take
+   a list of server hostnames instead of instance ids. However they can't be
+   mixed while running the command. Example: if you use hostnames, it would
+   have to be for all the nodes to delete.
+
 .. note::
   If you are :ref:`baremetal_provision` then follow those
   scale-down instructions to call ``openstack overcloud node delete`` with a