Based on a recent discussion of Chrome's cast device requery behavior, mfoltz@ would like to cache devices discovered on WiFi networks based on BSSID instead of SSID.  Although this hurts the mesh network case, this would bring device caching in line with Android's behavior, which is likely more important.  Furthermore, devices from an ethernet network should probably not be cached anymore.  This can probably be implemented by returning the "unknown" network ID for when ethernet connectivity is present, without changing CastMediaSinkServiceImpl.