Add property contexts for vts props

vts_config_prop and vts_status_prop are added to remove exported*_prop.
ro.vts.coverage becomes vts_config_prop, and vts.native_server.on
becomes vts_status_prop.

Bug: 155844385
Test: Run some vts and then getprop, e.g. atest \
      VtsHalAudioEffectV4_0TargetTest && adb shell getprop
Test: ro.vts.coverage is read without denials
Change-Id: Ic3532ef0ae7083db8d619d80e2b73249f87981ce
diff --git a/private/init.te b/private/init.te
index 7a2e0b3..49a98e0 100644
--- a/private/init.te
+++ b/private/init.te
@@ -59,3 +59,7 @@
 # SELinux hooks were detected.
 set_prop(init, init_perf_lsm_hooks_prop)
 neverallow { domain -init } init_perf_lsm_hooks_prop:property_service set;
+
+# Only init can write vts.native_server.on
+set_prop(init, vts_status_prop)
+neverallow { -init } vts_status_prop:property_service set;