api-ref: Fix parameters for os-volume-attachments.inc

In the following APIs, the 'volume_id' parameters are
'path' parameters. So fix them.

- GET /servers/{server_id}/os-volume_attachments/{volume_id}
- DELETE /servers/{server_id}/os-volume_attachments/{volume_id}

In addition, the descriptions of the parameters are amended.

Change-Id: Iab93acde31639b1471c83b06fb1a77474bb52c48
Closes-Bug: #1770560

api-ref/source/os-volume-attachments.inc

@@ -117,7 +117,7 @@ Request
 .. rest_parameters:: parameters.yaml
 
   - server_id: server_id_path
-  - volume_id: volume_id
+  - volume_id: volume_id_attached_path
 
 Response
 --------
@@ -189,7 +189,7 @@ Request
 .. rest_parameters:: parameters.yaml
 
   - server_id: server_id_path
-  - volume_id: volume_id
+  - volume_id: volume_id_to_detach_path
 
 Response
 --------

api-ref/source/parameters.yaml

@@ -337,12 +337,24 @@ tenant_id:
   in: path
   required: true
   type: string
+volume_id_attached_path:
+  description: |
+    The UUID of the attached volume.
+  in: path
+  required: true
+  type: string
 volume_id_path:
   description: |
     The unique ID for a volume.
   in: path
   required: true
   type: string
+volume_id_to_detach_path:
+  description: |
+    The UUID of the volume to detach.
+  in: path
+  required: true
+  type: string
 
 # variables in query
 access_ip_v4_query_server: