ANDROID: sdcardfs: Add sandbox

Android/sandbox is treated the same as Android/data

Bug: 27915347
Test: ls -l /sdcard/Android/sandbox/*somepackage* after
      creating the folder.
Signed-off-by: Daniel Rosenberg <drosen@google.com>

Change-Id: I7ef440a88df72198303c419e1f2f7c4657f9c170