Enable telephony fallback behavior in config.xml

Enable telephony fallback behavior in config.xml. After this change,
when geolocation detection is enabled, devices can use telephony
detection suggestions after a flight until a "certain" suggestion
has been made by the geolocation detection code.

Bug: 197624972
Test: build / boot / treehugger
Change-Id: I247992a1441310b8601cf563a4acdb84bbd6d097