Remove FUSE restriction blocking apps from making their dirs

Earlier implementation of FUSE had Android/ on the FUSE mount,
this resulted in vold hanging when apps called any of the
Context#getExternalFilesDir methods. With FUSE mounts,
we ensured in the FUSE handling that apps could always create their
dirs so they never needed the fallback to call into vold.

Now, Android/ will become an sdcardfs mount again and will have the
'default' bind mount view. We need to allow them call into vold when
they need to create their app dirs and don't have the right
permissions on the filesystem

Cleanup some unused code

Test: while true; do atest AdoptableHostTest; done
Bug: 135341433
Change-Id: Ic63de4f6d96e3d1012aa8bcfd2de09774362cfbc