fix: avoid resetting a learner schedule to before a course starts

If a learner changes modes (like upgrades to a verified learner),
we will reset their schedule for them. But if they did this before
the course started, we would accidentally set their schedule to
the current time. So when the course did start, they would already
appear to be behind schedule.

That's silly. So now we always look at course start time when
resetting the learner's schedule.

AA-426

openedx/features/course_experience/tests/views/test_course_outline.py

@@ -71,7 +71,7 @@ class TestCourseOutlinePage(SharedModuleStoreTestCase, MasqueradeMixin):
         # pylint: disable=super-method-not-called
         with super().setUpClassAndTestData():
             cls.courses = []
-            course = CourseFactory.create(self_paced=True)
+            course = CourseFactory.create(self_paced=True, start=timezone.now() - datetime.timedelta(days=1))
             with cls.store.bulk_operations(course.id):
                 chapter = ItemFactory.create(category='chapter', parent_location=course.location)
                 sequential = ItemFactory.create(category='sequential', parent_location=chapter.location, graded=True, format="Homework")  # lint-amnesty, pylint: disable=line-too-long