disable parallel asset compilation
disable parallel asset compilation

This threading is causing intermittent issues with Jammit failing, we're
going to disable it for now.

test plan: run rake canvas:compile_assets, it should succeeed.

Change-Id: I196ba8a1ba5bfb5b951c063519642ea25bb0f25c
Reviewed-on: https://gerrit.instructure.com/10902
Tested-by: Jenkins <d95b56ce41a2e1ac4cecdd398defd7414407cc08@instructure.com>
Reviewed-by: Cody Cutrer <c4fe2b1d90ef8f2548c8aeabfa633434316f0305@instructure.com>

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