VMware: spawn refactor - phase 1 - copy_virtual_disk

Move copy_virtual_disk to vm_util and change all copy_virtual_disk
in vmops to use it

partial blueprint vmware-spawn-refactor
Co-authored-by: Tracy Jones <tjones@vmware.com>

Change-Id: I0cda2bd465dc8a9de1b7ff4c1220e77b9c797471
Merge "VMware: spawn refactor - phase 1 - copy_virtual_disk"