update locked message on draft state discussions
update locked message on draft state discussions

fixes CNVS-8187

test plan:
  * in a course with draft state enabled, create a locked
    discussion (published w/ an available after date);
  * verify that the teacher view of the discussion does not
    change;
  * verify that as a student you see only the title of the
    discussion and a message that reads, "this topic is
    locked until <date>."

Change-Id: I8c7220752c337510b38802f37355c2583ba0287f
Reviewed-on: https://gerrit.instructure.com/28148
Tested-by: Jenkins <d95b56ce41a2e1ac4cecdd398defd7414407cc08@instructure.com>
Reviewed-by: Braden Anderson <a6cc2cef7d25f27847876bdb81651755fcebacf0@instructure.com>
QA-Review: Matt Fairbourn <5f353e1c97bb9cc046b9db20beca0b9392f6f1b2@instructure.com>
Product-Review: Zach Pendleton <514dbb4d54d4f29e454990df7d075678f43f92aa@instructure.com>

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