Although libnm filters out properties received from the daemon that it
doesn't understand, there may be other clients that do not. In
particular, a client might call GetSettings() on a connection, update
the ipv4.addresses property in the returned dictionary, and then pass
the dictionary to Update(). In that case, the updated dictionary would
contain ipv4.address-data, but it would not reflect the changes the
client intended to make.

Fix this by changing the daemon side to prefer the legacy properties
to the new ones if both are set, and changing the client side to not
send the legacy properties (since we don't support new clients talking
to old servers anyway).