Set globalize fallbacks for requests

New version of globalize uses RequestStore gem to store I18n.locale and
Globalize.fallbacks in a per request basis to avoid collissions between
different requests. This gem update broke Globalize.fallback results
because it tries to fetch fallbacks from RequestStore, where there is no
locale fallbacks definition.

spec/shared/features/translatable.rb

@@ -56,6 +56,22 @@ shared_examples "translatable" do |factory_name, path_name, input_fields, textar
       end
     end
 
+    scenario "should show first available fallback when current locale translation does not exist", :js do
+      attributes = fields.product(%i[fr]).map do |field, locale|
+        [:"#{field}_#{locale}", text_for(field, locale)]
+      end.to_h
+      translatable.update(attributes)
+      visit path
+
+      select "English", from: :translation_locale
+      click_link "Remove language"
+      select "Español", from: :translation_locale
+      click_link "Remove language"
+      click_button update_button_text
+
+      expect(page).to have_content "en Français"
+    end
+
     scenario "Add a translation", :js do
       visit path