UserDataPreparer: reboot to recovery for system user only am: fd31f740ce am: 7abafd53c9

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/17416118

Change-Id: I8b5b985cc351e60f0d660ac9ea00062ec7749597
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>