Close screenshot UI on CLOSE_SYSTEM_DIALOGS intent

Bug: 158845370
Fix: 158845370
Bug: 148808304
Test: manual -- tapped search bar, took a screenshot, and then
swiped up to home to verify that the home screen reappeared
correctly

Change-Id: I74d16e71392482185bb87d8f5d71ea93f38a40d6