Android USB reverse tethering: How to fool the apps
I'd say that there are only Mod specific solutions. Nearly every App that I know uses this Android API, and therefore the code snipped in your questions, for network connectivity checks.

One would need to change the Cyanogen source so that the OS (Android+Cyanogen) is aware of the USB reverse tethering network connectivity and returns the right information to app requesting the current network state. I don't believe that this can be done with some artificial layer between the API and the app that "fools" the app into this. It's more realistic that Cyanogen implements the handling of reverse tethering by imitating an active WiFi connection. You should ask them to address this topic.
Maybe in the future Android has official support for reverse tethering. :)