Classroom Monitor student status text displays Not Assigned

[geoffreykwan]

Description

When a student registers for a run but does not launch the run and their teacher manually places them in a new workgroup, their status for a step says "Not Assigned" but it should say something more accurate.

Steps to reproduce

1. Sign in as a student and register to a run but do not launch it
2. Sign in as a teacher
3. Open the Classroom Monitor for the run
4. Go to the "Manage Students" view
5. Click "Create a New Team"
6. Drag the student into that new team
7. Go to the "Grade By Step" view
8. Click on a step
9. Find the row for the new student. You will see their "Status" displayed as "Not Assigned" but it should probably say "No Work".

Another way to reproduce

1. Sign in as a teacher and create a run
2. Have students launch the run and add some work
3. Log in as the teacher and add a step with an Open Response component
4. All the students will have their "Status" displayed as "Not Assigned" for the new step. It will change to "No Work" once they launch the run again.

I think we determine what to display by looking at the student status object. If the student does not have a student status object for a run or does not have a status for a step, maybe we should display "No Work" instead of "Not Assigned". We want to make sure "Not Assigned" does show up in cases where there is branching and that student is not assigned to the steps in a specific branch path.