disable cross-shard conversations for the interim
disable cross-shard conversations for the interim

to reduce confusion

test plan:
 * go to conversations on a shard other than your own
 * it should redirect back to the dashboard with a helpful message

Change-Id: I083a7fcb88bb3abdc40ad0bbf45c24ac6f237886
Reviewed-on: https://gerrit.instructure.com/14080
Tested-by: Jenkins <d95b56ce41a2e1ac4cecdd398defd7414407cc08@instructure.com>
Reviewed-by: Jon Jensen <44f878afe53efc66b76772bd845eb65944ed8232@instructure.com>

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