don't pull assessment question from the same bank twice for the same quiz

fixes CNVS-16139, CNVS-17164

test plan:

  - as a teacher
    - create a quiz with two groups that both pull from the same bank
    - save and publish the quiz
    - take the quiz
    - you should never get the same question pulling from that bank twice

    - create a quiz with groups that contain questions (not from a bank)
    - save and publish the quiz
    - take the quiz
    - the questions should be pulled randomly from the group

  - test for regressions around building and taking quizzes with groups
    both with and w/o question banks in any permutation you can think of

Change-Id: Ia1d305cbc1e6051d38adcaff8e192d97802c6bd5
Reviewed-on: https://gerrit.instructure.com/45237
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Ryan Taylor <rtaylor@instructure.com>
QA-Review: Trevor deHaan <tdehaan@instructure.com>
Product-Review: Derek DeVries <ddevries@instructure.com>