Access DeviceConfig as system_server

This fixes SecurityException when statsd starts after
StatsCompanionService and sayHiToStatsd is called through statsdReady
Binder call from statsd.

Bug: 231382935
Bug: 232578561
Test: m
Test: flash and simulate statsd starting after StatsCompanionService
using adb shell statsd [stop|start]
Test: adb shell cmd stats print-uid-map

Ignore-AOSP-First: AOSP doesn't automerge into tm-dev. Cherry-pick to
AOSP in aosp/2098434

Change-Id: I5c9d9ddd5e433aa130eae34cfec811fa4f7ce580
1 file changed