Add default NetworkRecommendation to core.mk

This makes the apk avaiable on all devices and can be overridden on a
per-product basis using LOCAL_OVERRIDES_PACKAGES.

BUG: 33224286
Test: Verified with lunch aosp_bullhead-userdebug; make

Change-Id: Ib345193caa4431b6405294bd8759d93349335814