Makes new files search results read once per search

closes CNVS-16898

Test Plan:
  - Enable New Files
  - Go to New Files
  - Enable a Screenreader
  - Search for something
  - The results should be read to you.
  - Search for something else
  - Only results for your something else should be read.

Change-Id: Ia479e68e04d3d3285c0ccd1d27180e49bf90c5d2
Reviewed-on: https://gerrit.instructure.com/44461
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Ryan Shaw <ryan@instructure.com>
QA-Review: Jahnavi Yetukuri <jyetukuri@instructure.com>
Product-Review: Clay Diffrient <cdiffrient@instructure.com>