[baremetal] idf support for different board types

[baremetal] idf support for different board types

This modification enables having different models of target nodes
but restricts them to two groups of the same kind assuming:
 - 3 KVMs will be same model and have the same NIC names
 - 2 Compute nodes will be the same model and have same NIC names

This is an ad-hoc change for arm-pod7. Will work for all other setups
but the jinja2 logic should be evetually extended to support a per
board approach, allowing any board to be any kind

Change-Id: Ie994d661e3dbe5b9a33d290a850a6152cf320c86
Signed-off-by: Guillermo Herrero <guillermo.herrero@enea.com>