We trust any incoming value from the system UID, so we should also
trust values coming from the root UID, which includes many shell
commands such as "svc".
Bug: 193659633
Test: atest BluetoothInstrumentationTests:com.android.bluetooth.btservice.AdapterServiceTest --rerun-until-failure 100
Change-Id: Ied07731345f08fc3c4df465a3773e35c8df7c59a