Fix EC2 instance bdm response

Make the bdm response respect Amazon EC2 spec:
 * use ec2 volume id instead of uuid
 * use volume attach_status instead of status

References:
http://docs.aws.amazon.com/AWSEC2/latest/APIReference/ApiReference-ItemType-EbsInstanceBlockDeviceMappingResponseType.html

Resolves bug 1165973.

Change-Id: Ib68397b79f63e01e92ed4bebbc245ba5e0a3ad11
Merge "Fix EC2 instance bdm response"