Currently imageRef in server create, rebuild and rescue
operation can be accepted as random url which contains image
UUID and fetch the UUID from that.
As /images proxy APIs are deprecated, and ImageRef in
server creation etc are UUID only and valid against glance.
This patch makes imageRef handling as UUID only and
return 400 if non UUID are requested.
NOTE- Previously nova use to allow the empty string which was
ok in case of boot from volume.
We will keep the same behavior of allowing empty string in case of
boot from volume only and 400 in all other case.
Closes-Bug: #1607229
Change-Id: I49f4da62c1b5b3fd8c5f67039ae113f76722b26c
cbd3ec476f