Add a default root access mode.

Instead of relying on the Settings app code to assume a default,
actually set one

Change-Id: I2054bc0a793a79f7d26bc1bee23e097585a3b8c4
diff --git a/config/common.mk b/config/common.mk
index 4773dad..22be0b7 100644
--- a/config/common.mk
+++ b/config/common.mk
@@ -71,7 +71,8 @@
     ro.com.android.dataroaming=false
 
 PRODUCT_PROPERTY_OVERRIDES += \
-    ro.build.selinux=1
+    ro.build.selinux=1 \
+    persist.sys.root_access=1
 
 ifneq ($(TARGET_BUILD_VARIANT),eng)
 # Enable ADB authentication