NetworkManager template: add "StateReason" property to devices (#55)

NetworkManager supports the "State" and "StateReason" properties for
a long time. The "StateReason" redundantly also contains the state
value (for historic reasons).

In the past, NMClient's cache in libnm looked at the "State" property
to get the state. This is going to change (in 1.22) and libnm will consider
only at the "StateReason" for both properties. This change in libnm would
break dbusmock.

Note that NetworkManager/libnm didn't break API. The only thing that changes
is that libnm will require that "StateReason" property is present. The breakage
is caused by dbusmock not providing a perfect stub implementation of NetworkManager's
API.

See-also: https://gitlab.freedesktop.org/NetworkManager/NetworkManager/commit/ec39498fc6d70cf6887f08b4dfbc5cff021fc231

dbusmock/templates/networkmanager.py

@@ -321,6 +321,7 @@ def AddEthernetDevice(self, device_name, iface_name, state):
 
     props = {'DeviceType': dbus.UInt32(1),
              'State': dbus.UInt32(state),
+             'StateReason': (dbus.UInt32(state), dbus.UInt32(0)),
              'Interface': iface_name,
              'ActiveConnection': dbus.ObjectPath('/'),
              'AvailableConnections': dbus.Array([], signature='o'),
@@ -389,6 +390,7 @@ def AddWiFiDevice(self, device_name, iface_name, state):
                               'Driver': 'dbusmock',
                               'DeviceType': dbus.UInt32(2),
                               'State': dbus.UInt32(state),
+                              'StateReason': (dbus.UInt32(state), dbus.UInt32(0)),
                               'Interface': iface_name,
                               'IpInterface': iface_name,
                           })