Interactions with ModemManager

[Colin Helliwell <colin helliwell ln-systems com>]

A couple of things I've noticed in integrating NM with ModemManager:
1. It seems that eth0 doesn't come up - i.e. dhcp client not fired off - until MM has done it's startup 
operations on the GSM modem. It so happens that my GSM has a long power-on pause, and that is holding up the 
system's eth network start-up too. Not a huge problem as a hyper-fast startup isn't needed, but not ideal..
2. Even after the initial 'query' start-up on the GSM, NM seems to leave it enabled (as per mmcli -m 0), 
rather than leaving it disabled until called upon (with a nmcli conn up XX)

Any views please...?