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/service_contexts b/private/service_contexts
index b5e3407..7273676 100644
--- a/private/service_contexts
+++ b/private/service_contexts
@@ -207,6 +207,7 @@
 logd                                      u:object_r:logd_service:s0
 looper_stats                              u:object_r:looper_stats_service:s0
 lpdump_service                            u:object_r:lpdump_service:s0
+mdns                                      u:object_r:mdns_service:s0
 media.aaudio                              u:object_r:audioserver_service:s0
 media.audio_flinger                       u:object_r:audioserver_service:s0
 media.audio_policy                        u:object_r:audioserver_service:s0