add specs for using overridden dates on modules page for observers
add specs for using overridden dates on modules page for observers

turns out the code was already working, just needed some
specs to make sure for the case of observers

test plan:
* as an observer:
 * should see one due date, (the latest one)
  when not associated with a student

 * when associated with a student, should see the same
  due date that the student does

 * when associated with multiple students who have
  different dates applied to them, should see
  "Multiple Due Dates" indicator

closes #CNVS-2012

Change-Id: I358eb8433ff640bc9b7c15ab071b2b790ea2ce85
Reviewed-on: https://gerrit.instructure.com/16557
Tested-by: Jenkins <d95b56ce41a2e1ac4cecdd398defd7414407cc08@instructure.com>
Reviewed-by: Bracken Mosbacker <48b846001bca4166dc3fb7711563afc17525921e@instructure.com>
QA-Review: Bracken Mosbacker <48b846001bca4166dc3fb7711563afc17525921e@instructure.com>

va7map/canvas-lms,redconfetti/canvas-lms,SwinburneOnline/canvas-lms,shidao-fm/canvas-lms,redconfetti/canvas-lms,wye0220/shindig-canvas,djbender/canvas-lms,sdeleon28/canvas-lms,shidao-fm/canvas-lms,landonwilkins/canvas-lms,arrivu/qibla-ecampus,skmezanul/canvas-lms,instructure/canvas-lms,whalejasmine/canvas-lms,arrivu/jigsaw-lms,loganrun/pincan,wye0220/shindig-canvas,sfu/canvas-lms,sfu/canvas-lms,Rvor/canvas-lms,Unow/ins,narigone/canvas,nditech/red-innovadores-lms,instructure/canvas-lms,Unow/ins,sfu/canvas-lms,va7map/canvas-lms,arrivu/jigsaw-lms,samuels410/greatlakes-lms,jay3126/canvas-lms,antoniuslin/canvas-lms,juoni/canvas-lms,sdeleon28/canvas-lms,nditech/red-innovadores-lms,dgynn/canvas-lms,greyhwndz/canvas-lms,instructure/canvas-lms,arrivu/hoodemo,roxolan/canvas-lms,HotChalk/canvas-lms,rup/Tarrax,greyhwndz/canvas-lms,nditech/red-innovadores-lms,instructure/canvas-lms,Jyaasa/canvas-lms,jay3126/canvas-lms,narigone/canvas,utkarshx/canvas-lms,usmschuck/canvas,instructure/canvas-lms,tgroshon/canvas-lms,eCNAP/CANVAS,samuels410/greatlakes-lms,AndranikMarkosyan/lms,fronteerio/canvas-lms,kyroskoh/canvas-lms,gbleydon/canvas-lms,arrivu/arrivu-lms,wrdsb/canvas-lms,gbleydon/canvas-lms,sli7246/canvas_branch,leftplusrightllc/canvas-lms,merichar/canvas-lms,AndranikMarkosyan/lms,Unow/ins,eCNAP/CANVAS,grahamb/canvas-lms,usmschuck/canvas,narigone/canvas,kyroskoh/canvas-lms,loganrun/pincan,usmschuck/canvas,antoniuslin/canvas-lms,wye0220/shindig-canvas,dgynn/canvas-lms,whalejasmine/canvas-lms,ShreniiNepal/shrenii_lmp,Rvor/canvas-lms,antoniuslin/canvas-lms,dgynn/canvas-lms,utkarshx/canvas-lms,roxolan/canvas-lms,efrj/canvas-lms,sdeleon28/canvas-lms,sli7246/canvas_branch,usmschuck/canvas,ShreniiNepal/shrenii_lmp,venturehive/canvas-lms,sfu/canvas-lms,grahamb/canvas-lms,tgroshon/canvas-lms,utkarshx/canvas-lms,snehakachroo1/LSI_replica,HotChalk/canvas-lms,arrivu/qibla-ecampus,fronteerio/canvas-lms,roxolan/canvas-lms,matematikk-mooc/canvas-lms,ShreniiNepal/shrenii_lmp,leftplusrightllc/canvas-lms,landonwilkins/canvas-lms,wimemx/Canvas,HotChalk/canvas-lms,parbros/red-innovadores-lms,AndranikMarkosyan/lms,wrdsb/canvas-lms,matematikk-mooc/canvas-lms,snehakachroo1/LSI_replica,arrivu/arrivu-lms,leftplusrightllc/canvas-lms,efrj/canvas-lms,sfu/canvas-lms,whalejasmine/canvas-lms,arrivu/hoodemo,kyroskoh/canvas-lms,redconfetti/canvas-lms,eCNAP/CANVAS,skmezanul/canvas-lms,parbros/red-innovadores-lms,loganrun/pincan,eCNAP/CANVAS,wrdsb/canvas-lms,landonwilkins/canvas-lms,grahamb/canvas-lms,greyhwndz/canvas-lms,Unow/canvas-lms,samuels410/greatlakes-lms,Jyaasa/canvas-lms,Unow/canvas-lms,skmezanul/canvas-lms,gbleydon/canvas-lms,venturehive/canvas-lms,djbender/canvas-lms,matematikk-mooc/canvas-lms,djbender/canvas-lms,Unow/canvas-lms,AndranikMarkosyan/lms,Jyaasa/canvas-lms,antoniuslin/canvas-lms,va7map/canvas-lms,wimemx/Canvas,SwinburneOnline/canvas-lms,redconfetti/canvas-lms,landonwilkins/canvas-lms,venturehive/canvas-lms,efrj/canvas-lms,sli7246/canvas_branch,SwinburneOnline/canvas-lms,va7map/canvas-lms,SwinburneOnline/canvas-lms,Rvor/canvas-lms,samuels410/greatlakes-lms,arrivu/arrivu-lms,efrj/canvas-lms,juoni/canvas-lms,matematikk-mooc/canvas-lms,instructure/canvas-lms,wimemx/Canvas,instructure/canvas-lms,rup/Tarrax,skmezanul/canvas-lms,fronteerio/canvas-lms,merichar/canvas-lms,jay3126/canvas-lms,grahamb/canvas-lms,tgroshon/canvas-lms,kyroskoh/canvas-lms,juoni/canvas-lms,fronteerio/canvas-lms,parbros/red-innovadores-lms,snehakachroo1/LSI_replica,djbender/canvas-lms,Jyaasa/canvas-lms,juoni/canvas-lms,greyhwndz/canvas-lms,shidao-fm/canvas-lms,sdeleon28/canvas-lms,roxolan/canvas-lms,venturehive/canvas-lms,shidao-fm/canvas-lms,jay3126/canvas-lms,arrivu/hoodemo,grahamb/canvas-lms,rup/Tarrax,leftplusrightllc/canvas-lms,arrivu/jigsaw-lms,sfu/canvas-lms,sfu/canvas-lms,ShreniiNepal/shrenii_lmp,narigone/canvas,tgroshon/canvas-lms,nditech/red-innovadores-lms,HotChalk/canvas-lms,Rvor/canvas-lms,merichar/canvas-lms,arrivu/qibla-ecampus,snehakachroo1/LSI_replica,whalejasmine/canvas-lms,dgynn/canvas-lms,utkarshx/canvas-lms,wrdsb/canvas-lms