Merge "fs_mgr: Add OverlayMountPoints() to get the list of overlayfs backing storage" am: ec1b09fca9 am: 9a2bf07d51

Original change: https://android-review.googlesource.com/c/platform/system/core/+/1585166

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: I0b369a25d64eaf7005c2b3d7478530bc53fdb814