Automatically use correct lower paths for setupAppDir.

When we're asked to create an app directory, find the corresponding
volume, and use the raw path of that volume to create the directory.
This ensures this will continue working on devices that don't have
sdcardfs.

Bug: 146419093
Test: manual test on cuttlefish
Change-Id: I91d735c1adbcca171e5af73aca0abd7ef396d0b7
4 files changed