Allow mediaserver start transcoding service.

Bug: 187271658
Test: atest MediaTranscodeManagerTest; unit tests
Change-Id: I847a83ec3e0d852266b7b0c624767e72d48b45d5
diff --git a/private/property.te b/private/property.te
index 267ff85..01d4fd9 100644
--- a/private/property.te
+++ b/private/property.te
@@ -34,6 +34,7 @@
 system_internal_prop(userspace_reboot_test_prop)
 system_internal_prop(verity_status_prop)
 system_internal_prop(zygote_wrap_prop)
+system_internal_prop(ctl_mediatranscoding_prop)
 
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 ### Neverallow rules