Ignore wext wireless rtnetlink events

Ignore wext wireless rtnetlink events

The kernel wext core sends wireless events through the rtnetlink channel.
They show up with the ifi_change field set to 0.
The problem with those messages is that their ifi_flags might be
unsynchronized due to the fact that the actual message sending is handled
by a workqueue that doesnt build the message. ifi_flags is set to
dev_flags, but by the time the message is sent dev_flags might have changed.
Connman should just ignore those messages as we don't care about wext
events at all.