MediaMetricsService: Use system_clock for TimedAction am: 1b651bac83

Original change: https://android-review.googlesource.com/c/platform/frameworks/av/+/2996738

Change-Id: I15aea1057846a220bb22b249aed32dac39fbf128
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>