Add v3 api-ref for force delete snapshot

This patch is to add v3 api-ref for force delete a snapshot.

Change-Id: I44d16a9fa9065b5e92b18c487b45e7076ec03b0e

api-ref/source/v3/samples/snapshot-force-delete-request.json

@@ -0,0 +1,3 @@
+{
+    "os-force_delete": {}
+}

api-ref/source/v3/volumes-v3-snapshots-actions.inc

@@ -71,3 +71,36 @@ Request Example
 
 .. literalinclude:: ./samples/snapshot-status-update-request.json
    :language: javascript
+
+
+Force delete a snapshot
+~~~~~~~~~~~~~~~~~~~~~~~
+
+.. rest_method::  POST /v3/{project_id}/snapshots/{snapshot_id}/action
+
+Attempts to force delete a snapshot, regardless of state. Specify the
+``os-force_delete`` action in the request body.
+
+Response codes
+--------------
+
+.. rest_status_code:: success ../status.yaml
+
+   - 202
+
+
+Request
+-------
+
+.. rest_parameters:: parameters.yaml
+
+   - project_id: project_id_path
+   - snapshot_id: snapshot_id_path
+   - os-force_delete: os-force_delete
+
+
+Request Example
+---------------
+
+.. literalinclude:: ./samples/snapshot-force-delete-request.json
+   :language: javascript