Prevent Outcomes from being aligned to a rubric more than once
Prevent Outcomes from being aligned to a rubric more than once

closes OUT-4930
flag=none

Test plan:
- Go to Account > Outcomes and create two outcomes
("Outcome 1" and "Outcome 2")
- Go to Rubrics, click Add Rubric button, enter title
"Rubric 1", click Find Outcome link, select "Outcome 1",
click Import, then click Create Rubric button
- Verify that "Rubric 1" is created and its form is expanded
- Without reloading the page, click again Add Rubric button,
enter title "Rubric 2", click Find Outcome link, select
"Outcome 2", click Import, then click Create Rubric button
- Verify that "Rubric 2" is created and its form is expanded
- Verify that "Outcome 1" is aligned/listed in "Rubric 1" and
"Outcome 2" is aligned/listed in "Rubric 2"
- Click on edit icon for "Rubric 1", then click Find Outcome
link, select "Outcome 2", click Import, then click Update button
- Verify that now both "Outcome 1" and "Outcome 2" are
aligned/listed in "Rubric 1"
- Click on edit icon for "Rubric 2", then click Find Outcome
link, select "Outcome 2", click Import, then click Update button
- Verify that now both "Outcome 1" and "Outcome 2" are
aligned/listed in "Rubric 2"
- Click on edit icon for "Rubric 2", then click Find Outcome
link, select "Outcome 2", then click Import
- Verify that flash alert is displayed and that "Outcome 2"
remains aligned/listed only once in "Rubric 2"
- Click on edit icon for "Rubric 2", click Criterion link,
select "Outcome 2", then click Update Rubric button
- Verify that error box displays above Update Rubric button
- Click on Cancel button and verify that error box disappears
and "Rubric 2" reverts to non-editable form
- Go to Course > Outcome, create two outcomes, repeat the
above tests and verify that results are the same

Change-Id: Idfc89d46529318a45ea99c7d27e6ffbae435a460
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/302454
Tested-by: Service Cloud Jenkins <9144042a601061f88f1e1d7a1753ea3e2972119d@instructure.com>
Reviewed-by: Dave Wenzlick <1cd655a7a92f1469694e922643b036faede5d17f@instructure.com>
QA-Review: Dave Wenzlick <1cd655a7a92f1469694e922643b036faede5d17f@instructure.com>
Product-Review: Kyle Rosenbaum <08c6582752644f4eca90309d6d9805aeb3128ceb@instructure.com>

instructure/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,instructure/canvas-lms