Allow fabricated RROs to survive a reboot in non-user builds

Fabricated RROs created by shell are quite useful for debugging
purposes during development.  Allow them to persist in non-user
builds.

Test: $ adb shell cmd overlay fabricate --target android --name Test android:bool/test 0x12 1
      $ adb shell cmd overlay enable com.android.shell:Test
      $ adb shell cmd overlay list | grep Test
      --- com.android.shell:Test
Change-Id: I4dfdb451ae4ae8ffe745b56c325fa3ce304a78e1