Fix all the errors to get our tests green on Rails 5.1.

spec/controllers/admin/admin_controller_spec.rb

@@ -5,12 +5,14 @@ describe Admin::AdminController do
   context 'index' do
 
     it 'needs you to be logged in' do
-      expect { xhr :get, :index }.to raise_error(Discourse::NotLoggedIn)
+      expect do
+        get :index, format: :json
+      end.to raise_error(Discourse::NotLoggedIn)
     end
 
     it "raises an error if you aren't an admin" do
       user = log_in
-      xhr :get, :index
+      get :index, format: :json
       expect(response).to be_forbidden
     end