Makes DPM.getLogoutUser() and clearLogoutUser() system APIs.

They're used by CarService, which cannot use hidden APIs anymore.

Test: m update-api
Bug: 214336184
CTS-Coverage-Bug: 214336184

Change-Id: I7d11f0a2b75fa8b87a5a71d43ffc7adb8e84bc9c
2 files changed