Set media folder +F for adopted storage as well

We previously only set +F for /data/media, but adopted storage needs
this as well. Instead we add support for adding attrs to PrepareDir.

Bug: 163453310
Test: sm set-virtual-disk true
      follow UI setup and confirm +F on /mnt/expand/*/media
Change-Id: I08f13b57a4de3538e88b38eb95b0ac115a5a5ce8
3 files changed