Identify jump host bridges based on IDF / PDF nets

Identify jump host bridges based on IDF / PDF nets

- minor refactor of runtime templates parsing to allow var expansion;
- parse <pod_config.yml> into shell vars, match dynamically networks
  from PDF to IP addresses on bridges of current jumphost;
- keep old '-B' parameter in <ci/deploy.sh>, use it for providing
  fallback values in case there's no bridge name specified via IDF
  and no IP on the jumphost for one or more of the PDF networks;
- re-enable dry-run to ease testing of the above;
- add sample 'idf-pod1.yaml' to <mcp/config/labs/local>;

The new behavior will try to determine the jump host bridge names:
1. Based on IDF mapping, if available
2. Based on PDF network matching with IP addrs on jumphost;
3. Fallback to values passed via '-B';
4. Fallback to default values hardcoded in the deploy script;

Later, we will drop MaaS network env vars in favor of PDF vars,
once the PDF template is generating them.

Change-Id: If9cd65d310c02965b2e2bfa06a0d7e0f97f1dd48
Signed-off-by: Alexandru Avadanii <Alexandru.Avadanii@enea.com>