Allow Quizzes to save with Sync to SIS unchecked
Allow Quizzes to save with Sync to SIS unchecked

Fixes: SIS-2832

Test plan:
- Turn the following account settings on:
-- "Default SIS Sync for assignments, quizzes, grade discussion"
-- "Require assignment due date"
- Navigate to a course
- Create a Quiz
- Uncheck 'Post to SIS'
- Confirm you can save the quiz without a due date

Change-Id: Ieeb8d58b5287744148eec53e968370c6d361de59
Reviewed-on: https://gerrit.instructure.com/108933
Tested-by: Jenkins
QA-Review: Adrian Russell <5867b55c34ec258a06bcc4d9b6dbda2c79313b40@instructure.com>
Reviewed-by: Brad Humphrey <9233b6f5388d6867a2a7be14d8b4ba53c86cfde2@instructure.com>
Product-Review: Brad Humphrey <9233b6f5388d6867a2a7be14d8b4ba53c86cfde2@instructure.com>

instructure/canvas-lms,instructure/canvas-lms,djbender/canvas-lms,instructure/canvas-lms,venturehive/canvas-lms,djbender/canvas-lms,venturehive/canvas-lms,instructure/canvas-lms,djbender/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,venturehive/canvas-lms,venturehive/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,djbender/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,sfu/canvas-lms