Lesson: support unlimited max attempts

This issue only needs to be tested in 1 device. In the app, login as a student in master site. Open:  Lesson testing > Offline lessons > DOWNLOADABLE: Lesson with ALL questions and NO random jumps and UNLIMITED attempts . Open the top-right menu and download the lesson. Go offline and click to start the lesson (if you already started it before, click "No" to start it from the beginning). Click the button to go to the next page. Select "This is the wrong answer" and click Submit. Check that you see a button to try again. Click the button to try again. Check that you can answer the question again. You can repeat this process an unlimited number of times since the number of attempts is unlimited.