Merge "Fixed DPM.logoutUser() for headless system user mode." into sc-v2-dev am: f1f95597f0 am: 3ff4835584

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/16145450

Change-Id: I4701554c2145a53d2a6fdd2438462ebf0df48710