Submit the form after the image is attached

We were submitting the form without checking the AJAX request to attach
the image had finished, so sometimes two requests were executed at the
same time. Sometimes this made InvisibleCaptcha to go crazy and report
the form was submitted too quickly.

Checking the first AJAX request has finished before submitting the form
solves the problem.

spec/shared/system/nested_imageable.rb

@@ -182,6 +182,8 @@ shared_examples "nested imageable" do |imageable_factory_name, path, imageable_p
         Rails.root.join("spec/fixtures/files/clippy.jpg")
       )
 
+      expect(page).to have_selector ".loading-bar.complete"
+
       click_on submit_button
 
       expect(page).to have_content imageable_success_notice
@@ -197,6 +199,8 @@ shared_examples "nested imageable" do |imageable_factory_name, path, imageable_p
         Rails.root.join("spec/fixtures/files/clippy.jpg")
       )
 
+      expect(page).to have_selector ".loading-bar.complete"
+
       click_on submit_button
       imageable_redirected_to_resource_show_or_navigate_to