Use elapsedRealtime to measure in-progress app-ops

ElapsedRealtime is guaranteed monotonic, hence it won't jump back and
forth in time. currentTimeInMS might jump back in time effectively
causing a in-progress app-op with negative duration.

Test: TH
Fixes: 146853020
Change-Id: I6f4c1c29d651e39c914b5d00f88407abbedffe0c