Iteration on multi-user external storage.

Remove single-user bind mounts, since they need to remain as raw
mounts to correctly propagate when remounted.  This means we're back
to using sdcard_r GID to enforce READ_EXTERNAL_STORAGE.

Bug: 6925012
Change-Id: I41b5d7ddc985a5df2e288632a0a80d4724089e00
3 files changed