Fsync data after writing prefs am: 49170aa3e3 am: 4c0dcdaacb

Original change: https://android-review.googlesource.com/c/platform/system/update_engine/+/2320000

Change-Id: Ibfc332fdfb2292214180024c29cb6b1fa40ce5af
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>