Add a property to GNetworkMonitor indicating if the network
is metered, e.g. subject to limitations set by service providers.
The default value is FALSE
https://bugzilla.gnome.org/show_bug.cgi?id=750282
We were asking for properties on NM's dbus interface, but if NM is not
running then there won't be any. Check if the name has an owner before
doing anything to it.
https://bugzilla.gnome.org/show_bug.cgi?id=741653