spec: fix ordering of nulls for mysql in conversations spec
spec: fix ordering of nulls for mysql in conversations spec

refs CNVS-7032

Change-Id: I46f934990a89bbabf8348feca67969d6a2c24d29
Reviewed-on: https://gerrit.instructure.com/28609
Tested-by: Jenkins <d95b56ce41a2e1ac4cecdd398defd7414407cc08@instructure.com>
Reviewed-by: Nick Cloward <9cc571ed222c7ca8c35f018ff48a612f8cadeb73@instructure.com>
QA-Review: Cody Cutrer <c4fe2b1d90ef8f2548c8aeabfa633434316f0305@instructure.com>
Product-Review: Cody Cutrer <c4fe2b1d90ef8f2548c8aeabfa633434316f0305@instructure.com>

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