fix back button on discussion - fixes CNVS-2763
fix back button on discussion - fixes CNVS-2763

Change-Id: If32593aaf99da7e434c7040dffa50130e65a8c5b
Reviewed-on: https://gerrit.instructure.com/18127
Tested-by: Jenkins <d95b56ce41a2e1ac4cecdd398defd7414407cc08@instructure.com>
Reviewed-by: Zach Pendleton <514dbb4d54d4f29e454990df7d075678f43f92aa@instructure.com>
QA-Review: Cam Theriault <b4133c36b6d893d0872cc09e87b536d16aa2d241@instructure.com>

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