Allow appdomain read perms on apk_data_files.

Address:
type=1400 audit(0.0:103): avc: denied { read } for name="arm" dev="mmcblk0p28" ino=195471 scontext=u:r:untrusted_app:s0 tcontext=u:object_r:apk_data_file:s0 tclass=dir

(cherrypick of commit 711895db)

Bug: 16204150
Change-Id: I8bf0172b26b780c110c0d95c691785143acd7dd2