Allow shell and adbd access to media_rw_data_file for now.

With sdcardfs, we no longer have a separate sdcardd acting as
an intermediate between the outside world and /data/media.
Unless we modify sdcardfs to change contexts, we need these.

Remove this patch if sdcardfs is updated to change the
secontext of fs accesses.

Bug: 27925072
Change-Id: I3ad37c0f12836249c83042bdc1111b6360f22b3c