Update Scaling Deployments with Compute Cells  in line with the new network templates and network management without heat. 

• Update the `network_data.yaml` example

• Correct the steps that update the `network-environment.yaml`

• Remove the instructions to change the "name_lower"; as the 'provider:physical_network' defaults to the value of 'name_lower' in OSP17 there should not be a conflict with a different overcloud's "external" network.

Update in line with new bare metal provisioning process: 11.2. Provisioning bare metal overcloud nodes