Add delete_on_termination for compute API v2.79 - os-volume_attachments

This adds delete_on_termination field for the compute API response schema
for the 2.79 microversion in the following APIs:

  - GET /servers/{server_id}/os-volume_attachments (list)
  - GET /servers/{server_id}/os-volume_attachments/{volume_id} (show)
  - POST /servers/{server_id}/os-volume_attachments (attach)

Change-Id: I7a9b22477b800c6d60acb67c27aff5dcb61d7875
4 files changed