Merge "vold: Unmount StubVolume disks before unmounting EmulatedVolumes" into main am: 2f20c808c2

Original change: https://android-review.googlesource.com/c/platform/system/vold/+/2850049

Change-Id: Ib360884801c37c093d9836109f0b817987abd850
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>