Any interface not matching the convention: <interface>.<vlan id> will be
assumed to untagged when generating the config drive. The link type will
be set to `phy` in `network_data.json` instead of `vlan`. This prevents
invalid config drive configuration from being generated.

Change-Id: I00e7615581c7a214e0ee8e8f04cacdbb3ea4131a
Story: 2009910
Task: 44736