Cinder backup - Volume metadata inconsistency

After restoring a volume from backup, the metadata of target volume is same as source volume.
In the PowerMax driver we capture the device id of each volume in the metadata and 'copying' the target volumes metadata to the source will assign the incorrect device id to it

1. Created 2 volumes - non_boot_3 and non_boot_4.
2. Took a volume backup of non_boot_3.
3. Restored this backup to volume non_boot_4. The device ID of volume non_boot_3 is copied to non_boot_4. I think the device ID of non_boot_4 should not be changed.

The 2 volumes detail before restore. Please note that device IDs are 000F1 and 000F2 for the volumes.

| 819a7410-e578-442a-8b37-3f003a9aebe6 | non_boot_4 | available | 1 | BRON_89 | false | | ArrayID='00011111111', ArrayModel='VMAX250F', CompressionDisabled='False', Configuration='TDEV', DeviceID='000F2', DeviceLabel='OS-819a7410-e578-442a-8b37-3f003a9aebe6', Emulation='FBA', ReplicationEnabled='False', ServiceLevel='Bronze', Workload='None' |
| 59e40d21-2433-4f17-b459-82fb7dafd12d | non_boot_3 | available | 1 | BRON_89 | false | | ArrayID='000111111111', ArrayModel='VMAX250F', CompressionDisabled='False', Configuration='TDEV', DeviceID='000F1', DeviceLabel='OS-59e40d21-2433-4f17-b459-82fb7dafd12d', Emulation='FBA', ReplicationEnabled='False', ServiceLevel='Bronze', Workload='None' |

Created a backup for volume non_boot_3 as below.

| a8a3ebbe-8489-4896-a2dc-4976047fd337 | None | None | available | 1 | None | non_boot_3 | volumebackups |

Restored the backup to non_boot_4 as below.

stack@dldv0089:~$ ovb restore a8a3ebbe-8489-4896-a2dc-4976047fd337 non_boot_4
+-------------+--------------------------------------+
| Field | Value |
+-------------+--------------------------------------+
| backup_id | a8a3ebbe-8489-4896-a2dc-4976047fd337 |
| volume_id | 819a7410-e578-442a-8b37-3f003a9aebe6 |
| volume_name | non_boot_4 |
+-------------+--------------------------------------+

After restore, volume details as below. Please note that device ID is 000F1 for both the volumes.

| 819a7410-e578-442a-8b37-3f003a9aebe6 | non_boot_4 | available | 1 | BRON_89 | false | | ArrayID='00011111111', ArrayModel='VMAX250F', CompressionDisabled='False', Configuration='TDEV', DeviceID='000F1', DeviceLabel='OS-59e40d21-2433-4f17-b459-82fb7dafd12d', Emulation='FBA', ReplicationEnabled='False', ServiceLevel='Bronze', Workload='None', src_backup_id='a8a3ebbe-8489-4896-a2dc-4976047fd337' |
| 59e40d21-2433-4f17-b459-82fb7dafd12d | non_boot_3 | available | 1 | BRON_89 | false | | ArrayID='00011111111', ArrayModel='VMAX250F', CompressionDisabled='False', Configuration='TDEV', DeviceID='000F1', DeviceLabel='OS-59e40d21-2433-4f17-b459-82fb7dafd12d', Emulation='FBA', ReplicationEnabled='False', ServiceLevel='Bronze', Workload='None' |