The root UUID changes after a streamed partition image is written to
the block device, causing later deployment failure when assuming the
old UUID.
This change updates the root UUID after streaming the partition image
is complete.
This issue may have been missed in local testing because deploying the
same image repeatedly will result in stable root UUID across runs.
Change-Id: Ice4630c16fc216980488d1427f3b02e1b8a417fa
e61336602f