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
Merged-In: I08f13b57a4de3538e88b38eb95b0ac115a5a5ce8