Allow search/getattr 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.
Added for: system_server, dumpstate, and bluetooth

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

Bug: 27932396
Change-Id: I294cfe23269b7959586252250f5527f13e60529b