Utility script to merge new parameters into existing nic-config
templates. Uses process-templates.py rendered 'single-nic-vlans'
templates as reference and appends any parameters that is not
already present in the existing NIC template.
New NIC template parameters were introduced in:
https://review.openstack.org/#/c/580236/
When upgrading the existing NIC templates have to have these
new parameters merged.
Change-Id: I474e57878212d2cb7c2b392a5fdf4e449f783a66