Fix/vik/oe state

@Lyla-Fischer @natea Preliminary fix for open ended state changing.  Do not merge yet, for evaluation and comments only.

Description of the problem:

When someone authors a problem in studio (say a self assessment problem), and then some students try the problem and submit, and then the problem tasks are changed (say to self assessment then peer assessment), the problem will cause errors.  This is because the module stores its state.  If the tasks in the problem are changed, then the stored state no longer matches the defined state, so it can't parse. 

Solution:

Detect if the state is invalid.  If it is invalid, then overwrite the old state and start the problem fresh for the student.