sepolicy: allow system_server get dex2oat opt prop

Add policy allow system_server to read below properties:
ro.vendor.qti.cgroup_follow.enable
ro.vendor.qti.cgroup_follow.dex2oat_only

Fixing denial as below

E libc : Access denied finding property
"ro.vendor.qti.cgroup_follow.enable"

avc: denied { read } for comm="system_server"
name="u:object_r:vendor_default_prop:s0" dev="tmpfs" ino=24760
scontext=u:r:system_server:s0 tcontext=u:object_r:vendor_default_prop:s0
tclass=file permissive=0

CRs-Fixed: 2299439

Change-Id: Ib4a1414430d7585624450453b8c1df70b4fdd07b