Add log for debug

This CL use flag to decide which log should be show on.
This flag can be dynamic turn on when use below command:
adb shell setprop log.tag."your tag" VERBOSE

Bug: 155121301
Test: manually test
Change-Id: I0f3a28c11f6bd055efc84feb41d646b6c033f5b7

src/com/android/settings/bluetooth/BluetoothDeviceUpdater.java

@@ -52,7 +52,7 @@ import java.util.Map;
 public abstract class BluetoothDeviceUpdater implements BluetoothCallback,
         LocalBluetoothProfileManager.ServiceListener {
     private static final String TAG = "BluetoothDeviceUpdater";
-    private static final boolean DBG = false;
+    private static final boolean DBG = Log.isLoggable(TAG, Log.DEBUG);
 
     protected final MetricsFeatureProvider mMetricsFeatureProvider;
     protected final DevicePreferenceCallback mDevicePreferenceCallback;