This adds a --boot-from-volume option to the server create
command which is used with the --image or --image-property
option and will create a volume-backed server from the
specified image with the specified size. Similar to the
--volume option, the created root volume will not be deleted
when the server is deleted. The --boot-from-volume option
is not allowed with the --volume option since they both create
a block device mapping with boot_index=0.
Change-Id: I88c590361cb232c1df7b5bb010dcea307080d34c
Story: 2006302
Task: 36017
b9d6310556