config
Prior to this commit, if a user had configured a provisioner that had a
config with a `name` option, it would not properly set the top level
provisioner classes name config option which would lead to some
understanibly confusing results when trying to `--provision-with`. This
commit fixes that by checking to see if the top level name isn't set,
look to see if that provisioners config defines a name, and use that
instead.
711270b90a