Make notifier_api available at the correct url: /api/notifier

lms/urls.py

@@ -86,6 +86,7 @@ urlpatterns = [
     url(r'^user_api/', include('openedx.core.djangoapps.user_api.legacy_urls')),
 
     url(r'^notifier_api/', include('lms.djangoapps.discussion.notifier_api.urls')),
+    url(r'^/api/notifier/', include('lms.djangoapps.discussion.notifier_api.urls')),
 
     url(r'^i18n/', include('django.conf.urls.i18n')),