Merge "Support bind mounting volumes into other volume's mountpoint." am: 35eb1ae8

Original change: https://android-review.googlesource.com/c/platform/system/vold/+/2189643



Change-Id: I3e0528ff7a114971a8b6da9cc939c3de0de9fd4f
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>