Paginate backup list api

* Order list by updated at to show latest first
* Add pagination support for backup list and instance backup
  list
* Add tests for pagination and ordering

Implements: blueprint paginate-backup-list

Change-Id: Ie98bd2bc0500dfe4bbe0bb8b420ad80ad7f5a5df
server identifier corrected

Closes-Bug: #1262421

Change-Id: I41c907387e1ad3f2024a3dac21366a0f53e46f0f
Merge "Paginate backup list api"