Change currentTimeMillis to elapsedRealtime

System.currentTimeMillis does not gauntness to be monotonically
increasing, changed to SystemClock.elapsedRealtime

Bug: 38317243
Fixes: 38317243
Test: make -j 32; flash the angler device using local build

Change-Id: I75a70d43028e901d9f3459d6b525cac58e8e64af