The lookup_hiera_hash function is meant to lookup for the value
of a given key from a given Hiera hash. In the manifests this is
possible by saving the value of the hash in a variable first but
when driving lookups from the Heat templates we can't do it.
Change-Id: Ie31bb70314db44a0a18e86090cc74aa4df5de169
4e5ebf3ad8