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

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

Change-Id: I8a327d7bb4659b67d2ed3365b3640d88d9aee103