Code review comment for ~morphis/snappy-hwe-snaps/+git/network-manager:netplan-support

1) The network-setup-observe interface allows read-only access to /etc/netplan and /etc/network. We need it actually to check if the file /etc/netplan/00-default-nm-renderer.yaml exists to switch into the correct mode we're running the snap in.

2) 6730e78 isn't about disabling ethernet configuration. It sets the no-auto-default configuration item to prevent automatic network configuration of ethernet ports as this now done via the netplan configuration which is created automatically on first boot and maintained further inside console-conf.