CEC: Use thread-safe version for avr info

getSystemAudioMode() should have used the thread-safe method
to get the information of the connected AVR.

Bug: 18426137

Change-Id: Ib3edff97337b5960160dd39d551fbfbbfdfce93b

services/core/java/com/android/server/hdmi/HdmiCecLocalDeviceTv.java

@@ -765,7 +765,7 @@ final class HdmiCecLocalDeviceTv extends HdmiCecLocalDevice {
     }
 
     boolean isSystemAudioActivated() {
-        if (getAvrDeviceInfo() == null) {
+        if (!hasSystemAudioDevice()) {
             return false;
         }
         synchronized (mLock) {