Enable User HAL integration on automotive emulator.

Test: adb shell dumpsys car_service --hal UserHalService|grep user_hal_enabled

Bug: 163056008

Change-Id: I29a8715d3a16830dcc06f570f18a811559870016
diff --git a/common/car.mk b/common/car.mk
index b5993b3..fb557ba 100644
--- a/common/car.mk
+++ b/common/car.mk
@@ -81,10 +81,11 @@
 PRODUCT_COPY_FILES += \
   device/generic/car/common/preinstalled-packages-product-car-emulator.xml:$(TARGET_COPY_OUT_PRODUCT)/etc/sysconfig/preinstalled-packages-product-car-emulator.xml
 
-# Number of pre-created users
+# Multi-user properties
 PRODUCT_SYSTEM_DEFAULT_PROPERTIES := \
     android.car.number_pre_created_users=1 \
-    android.car.number_pre_created_guests=1
+    android.car.number_pre_created_guests=1 \
+    android.car.user_hal_enabled=true
 
 # Additional selinux policy
 BOARD_SEPOLICY_DIRS += device/generic/car/common/sepolicy