don't load audience enrollments for conversations index
don't load audience enrollments for conversations index

fixes CNVS-15886

test plan
- ensure that replying to a contextless conversation (from old
 conversations) still works. you'll have to make one using the
 console

Change-Id: Icdde36a0a2ed278523a293c960982bf317f5df12
Reviewed-on: https://gerrit.instructure.com/42048
Tested-by: Jenkins <d95b56ce41a2e1ac4cecdd398defd7414407cc08@instructure.com>
Reviewed-by: Brad Horrocks <7b5c5d1f2eba6c540b8e53f17d87a9bd7dbf604b@instructure.com>
QA-Review: Steven Shepherd <e794458448443812fb2685675aab3bbd1a3891bc@instructure.com>
Product-Review: Joel Hough <4816dabf8db1bc6cac35b3a24cab2ff844b5b0c7@instructure.com>

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