don't display account settings notification tab if empty
don't display account settings notification tab if empty

fixes CNVS-2684
fixes CNVS-2768

test plan:
- in the site admin account settings page:
  - the notification tab should be gone
  - updating settings should still work
- in the root account settings page:
  - the notifications tab should still be present and functional
- in a sub-account settings page:
  - the notification tab should be gone
  - updating settings should still work

Change-Id: Ic6b016be8d0b7a00f4153870220dbb34388a350b
Reviewed-on: https://gerrit.instructure.com/38367
Reviewed-by: Jeremy Stanley <b3f594e10a9edcf5413cf1190121d45078c62290@instructure.com>
Tested-by: Jenkins <d95b56ce41a2e1ac4cecdd398defd7414407cc08@instructure.com>
QA-Review: Anna Koalenz <8df3af669343a6e717fd7441a9deea414b21645f@instructure.com>
Product-Review: Simon Williams <088e16a1019277b15d58faf0541e11910eb756f6@instructure.com>

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