Updated openstack/openstack
Project: openstack/heat  c9a53dd659502be37f5d20fdab6c987d39854706

Remove validation of nested stack for preview

At preview time, resources have not been created and certain validation
do not apply (such as validating properties acquired from other
resources attributes), so this patch removes the validation of nested
stacks.

Closes-Bug: 1392455
Change-Id: I39be064c775369f1180487f4b48184e288734c49