Turn on headless system user ro property for cars.

Test: build
Bug: 130351531
Change-Id: I03404952bae0b99d01fd5e2097d5837618325d9d
diff --git a/car_product/build/car.mk b/car_product/build/car.mk
index 0fbed7d..5669aa8 100644
--- a/car_product/build/car.mk
+++ b/car_product/build/car.mk
@@ -50,8 +50,9 @@
     frameworks/av/media/libeffects/data/audio_effects.conf:system/etc/audio_effects.conf
 
 PRODUCT_PROPERTY_OVERRIDES += \
+    persist.bluetooth.enablenewavrcp=false \
     ro.carrier=unknown \
-    persist.bluetooth.enablenewavrcp=false
+    ro.fw.multiuser.headless_system_user=true
 
 # Overlay for Google network and fused location providers
 $(call inherit-product, device/sample/products/location_overlay.mk)