Add sepolicy for mdns service

mdns service is a subset of netd-provided services, so it gets
the same treatment as netd_service or dnsresolver_service

Bug: 209894875
Test: built, flashed, booted
Change-Id: I33de769c4fff41e816792a34015a70f89e4b8a8c
diff --git a/private/atrace.te b/private/atrace.te
index cbb5b7c..2ab8c69 100644
--- a/private/atrace.te
+++ b/private/atrace.te
@@ -33,6 +33,7 @@
   -installd_service
   -iorapd_service
   -lpdump_service
+  -mdns_service
   -netd_service
   -stats_service
   -tracingproxy_service