Wait for AJAX requests to complete so they don't blow up if they are only...

Wait for AJAX requests to complete so they don't blow up if they are only handled after DatabaseCleaner has already run

features/steps/project/merge_requests/acceptance.rb

@@ -20,10 +20,18 @@ class Spinach::Features::ProjectMergeRequestsAcceptance < Spinach::FeatureSteps
 
   step 'I should see the Remove Source Branch button' do
     expect(page).to have_link('Remove source branch')
+
+    # Wait for AJAX requests to complete so they don't blow up if they are
+    # only handled after `DatabaseCleaner` has already run
+    wait_for_ajax
   end
 
   step 'I should not see the Remove Source Branch button' do
     expect(page).not_to have_link('Remove source branch')
+
+    # Wait for AJAX requests to complete so they don't blow up if they are
+    # only handled after `DatabaseCleaner` has already run
+    wait_for_ajax
   end
 
   step 'There is an open Merge Request' do