Allow mediaserver start transcoding service.

Bug: 187271658
Test: atest MediaTranscodeManagerTest; unit tests
Change-Id: I847a83ec3e0d852266b7b0c624767e72d48b45d5
diff --git a/private/property_contexts b/private/property_contexts
index 5af4bb7..22a9075 100644
--- a/private/property_contexts
+++ b/private/property_contexts
@@ -168,6 +168,9 @@
 # Restrict access to stopping apexd.
 ctl.stop$apexd          u:object_r:ctl_apexd_prop:s0
 
+# Restrict access to starting media.transcoding.
+ctl.start$media.transcoding  u:object_r:ctl_mediatranscoding_prop:s0
+
 # Restrict access to restart dumpstate
 ctl.interface_restart$android.hardware.dumpstate u:object_r:ctl_dumpstate_prop:s0