No longer scrolls to top when item selected

For New Files.  Whenever an item was selected,
the page would scroll to the top (for the Files
page).  This has to do with how we were redrawing
and repainting the DOM for a11y.

fixes CNVS-17238

Test plan:
* Enable "Better File Browsing" feature flag
* Go to any course's Files page
* Make sure your browser window is small enough
  where you are required to scroll vertically
  to view the whole page
* Select an item in the file pane
* The browser should not scroll to the top
* The folder tree should still be accessible
  on Safari with VO enabled (see below)
* Refresh the page
* Behavior described above should remain intact

How to test for folder tree accessibilty:
(original test plan notes from the commit
that introduced the scrolling bug; this behavior
should still be occurring)
- Load up Better File Browsing
- Use Safari and VoiceOver and go to new files.
- Navigate to the folder listing.
- You should be able to navigate it with VO
- Refresh the page.  The same behavior should occur.
- Navigate into a subfolder. The same behavior should occur.

Change-Id: I619bd4cdded2178bf00c2b3d9d5ec123683d81ab
Reviewed-on: https://gerrit.instructure.com/45694
Reviewed-by: Clay Diffrient <cdiffrient@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: Jahnavi Yetukuri <jyetukuri@instructure.com>
Product-Review: Dan Minkevitch <dan@instructure.com>