Avoid race condition in system specs

Author: MrSerth

spec/system/messages_system_spec.rb

@@ -66,7 +66,10 @@
 
       it 'confirms the sender as a group member when clicking the grant access link' do
         view_inbox
-        expect { find("[href='#{grant_access_link}'").click }.to change { group.reload.confirmed_member? sender }.from(false).to(true)
+        expect do
+          find("[href='#{grant_access_link}'").click
+          wait_for_ajax
+        end.to change { group.reload.confirmed_member? sender }.from(false).to(true)
       end
 
       context 'when the group has been deleted' do