Do not include system overlay data when excluded

Do not include configurations or locales from overlays overriding system
resources when exclude_system is specified in GetResourceConfigurations
or GetResourceLocales.

Bug: 120083032
Test: run cts -m CtsContentTestCases -t
  android.content.res.cts.AssetManagerTest#testGetNonSystemLocales

Change-Id: I4ba3b07d3bb9ac72b196ff7ed4d1e853b51f7eea