Currently if you don't specify --deployment-user and for whatever reason
it's run as root (e.g. ansible as root using sudo), the deployment fails
because it attempts to write out to /home/root/. This change updates the
user home root lookup for clouds.yaml and throws a warning about setting
--deployment-user if it's root.
Change-Id: I284b374cc5e6d6a147286f0485832258f93f038f
(cherry picked from commit ff56863b26)