touch the attachment context after txn commit
touch the attachment context after txn commit

test plan: attachments should still upload and process as normal.
contexts should be touched after upload, for example if you upload a
file to a course, the course updated_at should change.

Change-Id: Ie05b535a0ae7638ffd66d60331d9bab9d2332dcc
Reviewed-on: https://gerrit.instructure.com/20584
Reviewed-by: Rob Orton <7e09c9d3e96378bf549fc283fd6e1e5b7014cc33@instructure.com>
Product-Review: Paul Hinze <4750e031e77b9a66270d86f487e0d12ea4126f1c@instructure.com>
QA-Review: Paul Hinze <4750e031e77b9a66270d86f487e0d12ea4126f1c@instructure.com>
Tested-by: Jenkins <d95b56ce41a2e1ac4cecdd398defd7414407cc08@instructure.com>

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