(NUI) Make "logout" link log you out w/out taking you to /logout page
(NUI) Make "logout" link log you out w/out taking you to /logout page

Fixes: CNVS-21436

Test Plan:
- Make sure the Use New Styles feature flag is ON
- Login to Canvas. On the side bar, select 'Account', then 'Logout'
- This should return you to the Canvas login screen. (Previously
  there was an intermediate form on a completely different /logout
  page that would ask to confirm the submission. You should not
  see this, but instead, arrive directly at the Canvas login page)

Change-Id: I9ef0f707078bc43ff4ea2f55cc1baee8d81288e6
Reviewed-on: https://gerrit.instructure.com/57455
Tested-by: Jenkins
Reviewed-by: Ryan Shaw <ea3cd978650417470535f3a4725b6b5042a6ab59@instructure.com>
QA-Review: Myller de Araujo <e5c7c5e1b7f2ce5e9870cc98ec52b20b3006cb48@instructure.com>
Product-Review: Colleen Palmer <387ba1943871e60965e6b44638a2f2e1ab9b8469@instructure.com>

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