Backup and restore bootable volume
Backup and restore bootable volume

The test verifies that when backuping a bootable volume,
the restored backup volume is also a bootable volume.

Added:
- Method for restoring a backup.

Change-Id: Ic94df97fd54e5671e487967b76894b48bc3e55ff

masayukig/tempest,openstack/tempest,cisco-openstack/tempest,Juniper/tempest,masayukig/tempest,Juniper/tempest,vedujoshi/tempest,vedujoshi/tempest,cisco-openstack/tempest,openstack/tempest