Following up on my own thread. We never found the solution to this,
but found a workaround. The controller loading order is the culprit,
so loading admin controllers first helps.
Added this to spec_helper.rb.
# warning: toplevel constant ExampleController referenced by
# admin controllers must load first to avoid global namespace
controllers to pollute the admin namespace
Dir[File.expand_path("app/controllers/admin/*.rb")].each do |file|