Merge "Add and use prepare_dir_with_policy() helper function" am: 14ac67efab

Original change: https://android-review.googlesource.com/c/platform/system/vold/+/2097184

Change-Id: I2d4d4a5832d66ded83e7f2effe14d34728d0db5d
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>