add alias for delayed posting from old delayed jobs
add alias for delayed posting from old delayed jobs

fixes CNVS-6143

test plan
- have some old delayed jobs that try to post a discussion using
 DiscussionTopic#try_posting_delayed
- ensure that they do indeed post the discussion

Change-Id: Ie3c2fa1e0ec65a031d4da258ce2d66be3a1cb7e1
Reviewed-on: https://gerrit.instructure.com/21248
Tested-by: Jenkins <d95b56ce41a2e1ac4cecdd398defd7414407cc08@instructure.com>
Reviewed-by: Jon Willesen <eb5ce5e6a76c243326fecfa94534101600f87bd9@instructure.com>
QA-Review: Cam Theriault <b4133c36b6d893d0872cc09e87b536d16aa2d241@instructure.com>
Product-Review: Joel Hough <4816dabf8db1bc6cac35b3a24cab2ff844b5b0c7@instructure.com>

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