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

Too questions based on updates to this merge proposal:

1. What does the functionality does the 'network-setup-observe' interface cover? Ideally this would be explained in the commit message, but as it's a one-liner, it's not clear.

2. Is commit 6730e78 still required? I thought with the addition of Scott's changes to write DHCP lease files to /run/NetworkManager/dhcp, and the associated change to probert, we no longer have to disable ethernet mgmt by NM.