Move multi-user OBB under user-specific path.

Support apps that may manually build OBB paths using
getExternalStorageDirectory() by making multi-user OBB paths live
under user-specific path.

This new structure means we can simplify the emulated_legacy paths
to be a single recursive bind mount.

Bug: 7212801
Change-Id: I85a0caebca52a6ff3bfe61c961518a91f0b8f8ff
1 file changed