don't use a raw array as a hash key
don't use a raw array as a hash key

it causes undefined behavior depending on the cache store,
especially with sharding

test plan:
 * load inbox on a non-default shard
 * it should work

Change-Id: I13c10f5f934543abc59cfd737eb9ed3b6b1fcdf5
Reviewed-on: https://gerrit.instructure.com/9969
Tested-by: Hudson <dfb64870173313a9a7b56f814c8e3b33e268497a@instructure.com>
Reviewed-by: Jon Jensen <44f878afe53efc66b76772bd845eb65944ed8232@instructure.com>

Unow/canvas-lms,skmezanul/canvas-lms,tgroshon/canvas-lms,SwinburneOnline/canvas-lms,antoniuslin/canvas-lms,tgroshon/canvas-lms,antoniuslin/canvas-lms,fronteerio/canvas-lms,greyhwndz/canvas-lms,arrivu/jigsaw-lms,shidao-fm/canvas-lms,samuels410/greatlakes-lms,ankithbti/canvas_lms,Rvor/canvas-lms,landonwilkins/canvas-lms,arrivu/jigsaw-lms,wrdsb/canvas-lms,fronteerio/canvas-lms,whalejasmine/canvas-lms,greyhwndz/canvas-lms,kyroskoh/canvas-lms,utkarshx/canvas-lms,wrdsb/canvas-lms,utkarshx/canvas-lms,Rvor/canvas-lms,venturehive/canvas-lms,shidao-fm/canvas-lms,Unow/canvas-lms,ankithbti/canvas_lms,fronteerio/canvas-lms,landonwilkins/canvas-lms,SwinburneOnline/canvas-lms,rup/Tarrax,arrivu/arrivu-lms,efrj/canvas-lms,wimemx/Canvas,va7map/canvas-lms,grahamb/canvas-lms,HotChalk/canvas-lms,djbender/canvas-lms,roxolan/canvas-lms,roxolan/canvas-lms,Jyaasa/canvas-lms,nditech/red-innovadores-lms,nditech/red-innovadores-lms,parbros/red-innovadores-lms,HotChalk/canvas-lms,leftplusrightllc/canvas-lms,wrdsb/canvas-lms,usmschuck/canvas,tgroshon/canvas-lms,HotChalk/canvas-lms,leftplusrightllc/canvas-lms,SwinburneOnline/canvas-lms,venturehive/canvas-lms,merichar/canvas-lms,sfu/canvas-lms,grahamb/canvas-lms,samuels410/greatlakes-lms,arrivu/hoodemo,landonwilkins/canvas-lms,grahamb/canvas-lms,Rvor/canvas-lms,jay3126/canvas-lms,roxolan/canvas-lms,leftplusrightllc/canvas-lms,juoni/canvas-lms,Unow/ins,wye0220/shindig-canvas,sfu/canvas-lms,efrj/canvas-lms,loganrun/pincan,skmezanul/canvas-lms,djbender/canvas-lms,sfu/canvas-lms,redconfetti/canvas-lms,greyhwndz/canvas-lms,sli7246/canvas_branch,usmschuck/canvas,merichar/canvas-lms,sdeleon28/canvas-lms,efrj/canvas-lms,va7map/canvas-lms,shidao-fm/canvas-lms,Jyaasa/canvas-lms,redconfetti/canvas-lms,rup/Tarrax,samuels410/greatlakes-lms,nditech/red-innovadores-lms,efrj/canvas-lms,Unow/ins,sli7246/canvas_branch,tgroshon/canvas-lms,djbender/canvas-lms,kyroskoh/canvas-lms,shidao-fm/canvas-lms,arrivu/hoodemo,skmezanul/canvas-lms,SwinburneOnline/canvas-lms,sfu/canvas-lms,wye0220/shindig-canvas,leftplusrightllc/canvas-lms,jay3126/canvas-lms,sfu/canvas-lms,jay3126/canvas-lms,grahamb/canvas-lms,ShreniiNepal/shrenii_lmp,jay3126/canvas-lms,rup/Tarrax,arrivu/qibla-ecampus,ankithbti/canvas_lms,em2/canvas-lms,sli7246/canvas_branch,arrivu/arrivu-lms,whalejasmine/canvas-lms,juoni/canvas-lms,merichar/canvas-lms,utkarshx/canvas-lms,antoniuslin/canvas-lms,wrdsb/canvas-lms,wimemx/Canvas,whalejasmine/canvas-lms,sdeleon28/canvas-lms,em2/canvas-lms,kyroskoh/canvas-lms,usmschuck/canvas,parbros/red-innovadores-lms,kyroskoh/canvas-lms,redconfetti/canvas-lms,arrivu/jigsaw-lms,Rvor/canvas-lms,nditech/red-innovadores-lms,redconfetti/canvas-lms,ShreniiNepal/shrenii_lmp,ShreniiNepal/shrenii_lmp,antoniuslin/canvas-lms,sdeleon28/canvas-lms,loganrun/pincan,djbender/canvas-lms,wye0220/shindig-canvas,arrivu/qibla-ecampus,va7map/canvas-lms,juoni/canvas-lms,roxolan/canvas-lms,greyhwndz/canvas-lms,whalejasmine/canvas-lms,venturehive/canvas-lms,arrivu/arrivu-lms,landonwilkins/canvas-lms,sdeleon28/canvas-lms,venturehive/canvas-lms,grahamb/canvas-lms,usmschuck/canvas,arrivu/qibla-ecampus,loganrun/pincan,wimemx/Canvas,Unow/canvas-lms,samuels410/greatlakes-lms,parbros/red-innovadores-lms,em2/canvas-lms,HotChalk/canvas-lms,ShreniiNepal/shrenii_lmp,utkarshx/canvas-lms,va7map/canvas-lms,Unow/ins,arrivu/hoodemo,Jyaasa/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,fronteerio/canvas-lms,skmezanul/canvas-lms,Jyaasa/canvas-lms,juoni/canvas-lms