Merge "Clarification for PREPARE_UNATTENDED_REBOOT_ERROR" am: 11773facb7 am: 8e7f7303cf

Original change: https://android-review.googlesource.com/c/platform/frameworks/base/+/1613109

Change-Id: I8636f713d0c81e8b7796e24efa7b41e3b17ede86