shill: Workaround shill crashing on closing network options.

This returns a valid DBus path for AddIPConfig and should avoid the crash. A
proper fix would be required at some point.

BUG=chromium-os:24918
TEST=build

Change-Id: Id45f5c121ba1ba44347b343c7a9f1ab934e9bfa1
Reviewed-on: https://gerrit.chromium.org/gerrit/15661
Tested-by: Darin Petkov <petkov@chromium.org>
Reviewed-by: Eric Shienbrood <ers@chromium.org>
Commit-Ready: Darin Petkov <petkov@chromium.org>
diff --git a/device_dbus_adaptor.cc b/device_dbus_adaptor.cc
index 2b1b24e..7049b20 100644
--- a/device_dbus_adaptor.cc
+++ b/device_dbus_adaptor.cc
@@ -93,7 +93,7 @@
 
 ::DBus::Path DeviceDBusAdaptor::AddIPConfig(const string& ,
                                             ::DBus::Error &/*error*/) {
-  return ::DBus::Path();
+  return "/";
 }
 
 void DeviceDBusAdaptor::Register(const string &network_id,