wwan/ofono: pass the right argument to manager proxy callback

Otherwise it will be dereferencing NULL when invoked.

Fixes: 58712c9546 ('ofono: take D-Bus proxy for ConnectionManager asynchronously')

https://github.com/NetworkManager/NetworkManager/pull/313
(cherry picked from commit 90fe78eb7f)
(cherry picked from commit 4d4b3fc8b5)

src/devices/wwan/nm-modem-ofono.c

@@ -664,7 +664,7 @@ handle_connman_iface (NMModemOfono *self, gboolean found)
 		                          OFONO_DBUS_INTERFACE_CONNECTION_MANAGER,
 		                          priv->connman_proxy_cancellable,
 		                          _connman_proxy_new_cb,
-		                          NULL);
+		                          self);
 	}
 }