TelephonyProvider: Fix Default APN Preference Overlay on 1st Boot

In the current code on CM13, the overlay preference can only be
called when Reset APN Settings is called.

Looking at the source history this is a regression. Comparing with
history, I've restored reading the overlay and tested that the
default preference is now marked on the first boot.

Change-Id: I3141d486afd45405c57ed25a89d9fa838fadf794
1 file changed