better show loading state when testing a policy

passbook/admin/templates/administration/policy/test.html

@@ -9,3 +9,18 @@
 {% block action %}
 {% trans 'Test' %}
 {% endblock %}
+
+{% block beneath_form %}
+<p class="loading" style="display: none;">
+  <span class="spinner spinner-xs spinner-inline"></span> {% trans 'Processing, please wait...' %}
+</p>
+{% endblock %}
+
+{% block scripts %}
+{{ block.super }}
+<script>
+  $('form').on('submit', function () {
+    $('p.loading').show();
+  })
+</script>
+{% endblock %}