The spec for support rebuild volume backed
server was accepted in Stein, but some of
the work did not finish, so repropose it
for Train.
Co-Authored-By: ramboman <lijie@unitedstack.com>
blueprint volume-backed-server-rebuild
Previously-approved: Stein
Change-Id: Iadb1898af2eb8ce5ecf0984dea7de729d982b29a