leave context host for attachment_json in reports
leave context host for attachment_json in reports

attachment_json will do this for you.
this prevents double  context information from the
merge of options in attachment_json

refs CNVS-10842

test plan
 - run report with canvas on port 3000
 - report object response should have the correct
   attachment download url

Change-Id: I58caffede266dee157afab63fd82a0a4a4bd5213
Reviewed-on: https://gerrit.instructure.com/40638
QA-Review: Dave Jungst <bfcdf3e6ca6cef45543bfbb57509c92aec9a39fb@instructure.com>
Tested-by: Jenkins <d95b56ce41a2e1ac4cecdd398defd7414407cc08@instructure.com>
Reviewed-by: Jeremy Stanley <b3f594e10a9edcf5413cf1190121d45078c62290@instructure.com>
Product-Review: Rob Orton <7e09c9d3e96378bf549fc283fd6e1e5b7014cc33@instructure.com>

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