Update API-REF for the cluster-del-node API

Change-Id: I4bad74991a03b6d22b3d23d6f993318df6452db1

api-ref/source/clusters.inc

@@ -577,6 +577,7 @@ Request Parameters
   - cluster_id: cluster_id_url
   - action: action_request
   - nodes: cluster_member_nodes
+  - destroy_after_deletion: destroy_after_deletion
 
 
 The ``action_name`` in the request body has to be ``del_nodes``.

api-ref/source/parameters.yaml

@@ -651,6 +651,13 @@ desired_capacity:
     The desired capacity of a cluster. When creating a cluster, this value is
     set to 0 by default.
 
+destroy_after_deletion:
+  type: boolean
+  in: body
+  required: False
+  description: |
+    Whether deleted nodes to be destroyed right away.
+
 domain:
   type: UUID
   in: body

api-ref/source/samples/cluster-del-nodes-request.json

@@ -3,6 +3,7 @@
         "nodes": [
             "aff0135",
             "e28a207"
-	]
+        ],
+        "destroy_after_deletion": false
     }
 }

doc/source/developer/cluster.rst

@@ -373,6 +373,9 @@ associated resources.
 Note also that by default Senlin won't destroy the nodes that are deleted
 from the cluster. It simply removes the nodes from the cluster so that they
 become orphan nodes.
+Senlin also provides a paramater ``destroy_after_deletion`` for this action
+so that a user can request the deleted node(s) to be destroyed right away,
+instead of becoming orphan nodes.
 
 
 Replacing Nodes in a Cluster