Allow installd to stat asec files and /data/media files.

Addresses denials such as:
avc: denied { getattr } for comm="installd" path="/data/app-asec/com.vectorunit.red-1.asec" dev="dm-0" ino=578229 scontext=u:r:installd:s0 tcontext=u:object_r:asec_image_file:s0 tclass=file

avc:  denied  { getattr } for  pid=262 comm="installd" path="/data/media/0/Android/data/com.google.android.apps.maps/cache/cache_vts_tran_base_GMM.m" dev="dm-0" ino=124930 scontext=u:r:installd:s0 tcontext=u:object_r:media_rw_data_file:s0 tclass=file

Change-Id: I406f1bea32736e2277adae1629a879fac0d714b6
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>