network: ignore unrecognized/irrelevant devices/connections

Don't log a warning if an unrecognized device type is seen.

Don't show slave connections in the menu. (Eg, don't show the
individual wired connections making up a bond, since they can't be
used individually.)

Make the icon only reflect the status of connections that are visible
in the menu. (ie, don't show the "connecting" icon when an
unrecognized connection type is connecting, and don't show a
"connected" status if the only active connections are of unrecognized
types.)

https://bugzilla.gnome.org/show_bug.cgi?id=682364