Only add accessibility actions in Overview if not in select mode

When modalness is >0, the user is in select mode and the icon menu is
hidden, therefore Talkback shouldn't pick it up.

Fix: 320203664
Flag: NONE bugfix
Test: Manual. Turn Talkback on, navigate to Overview, enter select mode,
 select the whole TaskView, Talkback shouldn't have any accessibility
 actions to execute.
Change-Id: I83dffce60f42cc32d83c499dfb08ddf97888f527