CARDS-2510: Fix computed questions always recalculating on checkin

[acrowthe]

• Fix computed questions being recalculated by the backend whenever the front end submits the a form with no relevant changed answers

To ensure that computed questions are working as expected:

• Launch in runmode test with --dev enables

• Sign in to user: computedtestuser password: testpassword

• Create a Backend Computed Question form but do not input any answers or save it

• Check the created form using composum. It should have 2 sections, one with 4 answers and one with 8 answers.

  • Check the section with 8 answers: Two should have strings describing the (lack of) values in Question 4
    

• Save the form with no edited answers

• Create a new Backend Computed Question form, fill out all answers and save it.

• Sign out of computedtestuser and sign into admin

• View the created forms in view mode only and verify that the answers are as expected

To ensure that the computed questions are only being recalculated when desired:

• Launch cards in runmode test with --dev and a debugger attached
• Put breakpoints on ComputedAnswersEditor.computeAnswers on lines 194 and 199 as shown below:
  
• Verify that the line 194 breakpoint is being hit whenever the computation shouldn't be saved
• Verify that the line 199 breakpoint is being hit whenever the computation should be saved:
  • When a form is created all computed questions should be calculated
  • When the question does not take any other question inputs (seen by 1 question always computing with result=1)
  • When the form is modified by a user that does not have access to the computed questions and modifies an input answer

[sashaandjic]

tested up to the Launch cards in runmode test with --dev and a debugger attached point in testing instructions