Allow kernel to read asec_image_file.

Address the following denial encountered when installing a forward-locked apk.

 W loop0   : type=1400 audit(0.0:36): avc: denied { read } for path="/data/app-asec/smdl1061145377.tmp.asec" dev="mmcblk0p28" ino=180226 scontext=u:r:kernel:s0 tcontext=u:object_r:asec_image_file:s0 tclass=file

Bug: 19936901
Change-Id: I829858564a8f89677b2bb4cbd4c8fe4250ae51de