Optimizing notify_credentials management command

** This removes some of the extra
   celery calls to credential service for
   updating grade when a certificate is updated.

** This removes extra db calls
   by reusing existing queryset values.

PROD-1363

openedx/core/djangoapps/credentials/management/commands/notify_credentials.py

@@ -212,6 +212,7 @@ class Command(BaseCommand):
     def send_notifications(self, certs, grades, site_config=None, delay=0, page_size=0, verbose=False):
         """ Run actual handler commands for the provided certs and grades. """
 
+        course_cert_info = {}
         # First, do certs
         for i, cert in paged_query(certs, delay, page_size):
             if site_config and not site_config.has_org(cert.course_id.org):
@@ -231,8 +232,14 @@ class Command(BaseCommand):
                 'status': cert.status,
                 'verbose': verbose,
             }
+
+            data = {
+                'mode': cert.mode,
+                'status': cert.status
+            }
+
+            course_cert_info[(cert.user.id, str(cert.course_id))] = data
             handle_course_cert_changed(**signal_args)
-            handle_cert_change(**signal_args)
 
         # Then do grades
         for i, grade in paged_query(grades, delay, page_size):
@@ -246,14 +253,21 @@ class Command(BaseCommand):
             )
 
             user = User.objects.get(id=grade.user_id)
+
+            # Grab mode/status from cert call
+            if course_cert_info:
+                key = (user.id, str(grade.course_id))
+                mode = course_cert_info[key].get('mode', None)
+                status = course_cert_info[key].get('status', None)
+
             send_grade_if_interesting(
                 user,
                 grade.course_id,
-                None,
-                None,
+                mode,
+                status,
                 grade.letter_grade,
                 grade.percent_grade,
-                verbose=verbose
+                verbose=verbose,
             )
 
     def get_course_keys(self, courses=None):

openedx/core/djangoapps/credentials/management/commands/tests/test_notify_credentials.py

@@ -127,7 +127,6 @@ class TestNotifyCredentials(TestCase):
         call_command(Command(), '--start-date', '2017-02-01')
         self.assertEqual(mock_grade_cert_change.call_count, 2)
         self.assertEqual(mock_grade_interesting.call_count, 2)
-        self.assertEqual(mock_program_changed.call_count, 2)
 
     @mock.patch(COMMAND_MODULE + '.time')
     def test_delay(self, mock_time):
@@ -154,15 +153,13 @@ class TestNotifyCredentials(TestCase):
         self.assertEqual(len(connection.queries), baseline + 2)  # one extra page query each for certs & grades
 
     @mock.patch(COMMAND_MODULE + '.send_grade_if_interesting')
-    @mock.patch(COMMAND_MODULE + '.handle_cert_change')
-    def test_site(self, mock_grade_interesting, mock_cert_change):
+    def test_site(self, mock_grade_interesting):
         site_config = SiteConfigurationFactory.create(
             site_values={'course_org_filter': ['testX']}
         )
 
         call_command(Command(), '--site', site_config.site.domain, '--start-date', '2017-01-01')
         self.assertEqual(mock_grade_interesting.call_count, 1)
-        self.assertEqual(mock_cert_change.call_count, 1)
 
     @mock.patch(COMMAND_MODULE + '.Command.send_notifications')
     def test_args_from_database(self, mock_send):