Attribute grade overrides from proctoring to the final reviewer

More generally, makes it so we don't ever pull in the user to whom
we're attributing overrides from the request, but always use the one
passed in via method parameters

Also pass through comments, if they're provided via this method

JIRA:EDUCATOR-4641

lms/djangoapps/grades/services.py

@@ -29,7 +29,7 @@ class GradesService(object):
 
     def override_subsection_grade(
             self, user_id, course_key_or_id, usage_key_or_id, earned_all=None, earned_graded=None,
-            feature=api.constants.GradeOverrideFeatureEnum.proctoring
+            feature=api.constants.GradeOverrideFeatureEnum.proctoring, overrider=None, comment=None
     ):
         """
         Creates a PersistentSubsectionGradeOverride corresponding to the given
@@ -46,7 +46,9 @@ class GradesService(object):
                                              usage_key_or_id,
                                              earned_all=earned_all,
                                              earned_graded=earned_graded,
-                                             feature=feature)
+                                             feature=feature,
+                                             overrider=overrider,
+                                             comment=comment)
 
     def undo_override_subsection_grade(self, user_id, course_key_or_id, usage_key_or_id,
                                        feature=api.constants.GradeOverrideFeatureEnum.proctoring):