Don't read /data/local.prop on user builds

Creating a root owned /data/local.prop is one of the most common
ways to root an Android device. /data/local.prop is only intended
to assist developers on debuggable devices, and is never
intended to be used on production devices.

Change-Id: Ifcfa21c2ee9914b0b54445218b4cf0fea0a98e9c