This commit allows admin to list/show cinder volume backups
using horizon dashboard and the user can perform the
following table action :
1. backup-restore
2. backup-delete
3. update backup-state
4. backup force-delete
Implements https://blueprints.launchpad.net/horizon/+spec/add-volume-backups-support-for-admin-panel
Change-Id: I2fea140a972eb4bd4f18ad1c83cfa4df58c23f6c