Update to nic settings not reflected in overcloud network config

[Wojciech Dec]

Description of problem:
On an active overcloud deployment, changes to the nic-template settings on the director are not reflected on the overcloud nodes. The original configuration continues to be pushed out.
Changes to the nic-template settings requires a deletion and redeployment of the overcloud to become effective, which is severely disruptive. Any changes to the network settings

Version-Release number of selected component (if applicable):
This was observed with both Newton and Pike

How reproducible:

Easily

Steps to Reproduce:
1. Start with default nic-template (templates/nic-configs/controller.yaml) suitable for the deployment and deploy the overcloud.
2. Modify the compute or controller nic-template configuration on the director node, eg
change the name of the bridge or the host interface to bridge association
3. Re-Run the deployment/update

Actual results:
/etc/os-net-config/element_config.json (Pike) or cat /etc/os-net-config/config.json (Newton) both contain the same info as pushed in step 1, after step 3.

Expected results:
The os-net-config json config should be updated to the latest settings

Additional info:
We have also tried deleting the json config file on the overcloud nodes, but the same, not updated one keeps on being pushed back.

[Jill Rouleau (jillrouleau)]

By default heat only applies network config on stack CREATE.
https://github.com/openstack/tripleo-heat-templates/blob/master/puppet/role.role.j2.yaml#L113

If you supply an additional environment file that looks like:
$ cat network-deployment-actions-update.yaml
parameter_defaults:
  NetworkDeploymentActions:
    - CREATE
    - UPDATE

network config changes should then be applied to an existing stack (on UPDATE).