VMware: Set virtual disk UUID to volume ID

VMware: Set virtual disk UUID to volume ID

The symlinks in /dev/disk/by-id/ (in a Linux guest OS running in VMware
ESX based Nova instance) use UUID of virtual disk as the SCSI device ID
when disk.EnableUUID is set to True in the virtual machine configuration
file. This patch sets the UUID of virtual disk corresponding to a Cinder
volume (at the time of volume creation) to volume ID so that end-users
(of Nova instance) can identify the device corresponding to an attached
volume in the guest using /dev/disk/by-id symlink.

For example, given a Cinder volume with ID = xyz, user can identify the
device corresponding to the volume in instance's guest using the symlink
/dev/disk/by-id/scsi-xyz provided disk.EnableUUID is set to True in the
instance's virtual machine configuration file (in ESX).

Note: If the UUID of the virtual disk corresponding to a volume is unset
at the time of volume creation, a random UUID will be used.

Closes-Bug: #1475738
Change-Id: I8f9d210083010b25833a7b108ae135417c72fd09