When a 464xlat upstream disconnects, onLinkPropertiesChanged is
called after onLost. This breaks an UpstreamNetworkMonitor
assumption that no callback will ever arrive after onLost.
Bug: 173068192
Fix: 185117377
Test: new unit test
Change-Id: I4ff1eca6d5ed1680ff716c71b683891c8a0e5a77