correct check for enrollment on an entitlement

[LEARNER-4484]

openedx/core/djangoapps/catalog/utils.py

@@ -389,13 +389,17 @@ def get_fulfillable_course_runs_for_entitlement(entitlement, course_runs):
     search_time = datetime.datetime.now(UTC)
     for course_run in course_runs:
         course_id = CourseKey.from_string(course_run.get('key'))
-        is_enrolled = CourseEnrollment.is_enrolled(entitlement.user, course_id)
+        (user_enrollment_mode, is_active) = CourseEnrollment.enrollment_mode_for_user(
+            user=entitlement.user,
+            course_id=course_id
+        )
+        is_enrolled_in_mode = user_enrollment_mode == entitlement.mode
         if is_course_run_entitlement_fulfillable(course_id, entitlement, search_time):
-            if (is_enrolled and
+            if (is_enrolled_in_mode and
                     entitlement.enrollment_course_run and
                     course_id == entitlement.enrollment_course_run.course_id):
                 enrollable_sessions.append(course_run)
-            elif not is_enrolled:
+            elif not is_enrolled_in_mode:
                 enrollable_sessions.append(course_run)
 
     enrollable_sessions.sort(key=lambda session: session.get('start'))