bootstat: Fix the SELinux policy after removing domain_deprecated.

* Allow reading /proc.

type=1400 audit(1453834004.239:7): avc: denied { read } for pid=1305
comm="bootstat" name="uptime" dev="proc" ino=4026536600
scontext=u:r:bootstat:s0 tcontext=u:object_r:proc:s0 tclass=file
permissive=0

* Define domain for the /system/bin/bootstat file.

init: Service exec 4 (/system/bin/bootstat) does not have a SELinux
domain defined.

Bug: 21724738
Change-Id: I4baa2fa7466ac35a1ced79776943c07635ec9804