Refresh runningTaskView's thumbnail after setting shouldShowScreenshot to true

- TaskThumbnailViewDeprecated won't redraw automatically unless refresh() is called

Fix: 346696742
Test: Invoke Omnient or Screenshot hardware button on live tile, verify running task switches to screenshot after overlay closes
Test: Select/Screenshot swithces to screenshot normally
Flag: EXEMPT BUG_FIX
Change-Id: I678fb155bd577afbacfde7233956ce6cfa5e569d