Controller: Exec puppet after all configuration

Controller: Exec puppet after all configuration

This patch adds a new ControllerNodesPostDeployment resource
which can be used along with the environment file to
specify a nested stack which is guaranteed to execute
after all the Controller config (HA, or other) have
executed.

This is really useful for Puppet in that Heat actually
controls where puppet executes in the deployment
process and we want to ensure puppet runs after
all hiera configuration data has be deployed to
the nodes. With the previous approach some of the
data would be there, but most of the HA data which
actually gets composed outside of the controller-puppet.yaml
nested stack would not be guaranteed to be there in time.

As os-apply-config (tripleo-image-elements) have their
ordering controlled within the elements themselves an empty stubbed
in nested stack has been added so that we don't break that
implementation.

Partial-bug: 1418805

Change-Id: Icd6b2c9c1f9b057c28649ee3bdce0039f3fd8422