Pin HUNs while guts are visible

Test: NotificationGutsManagerTest
Test: long press HUN - verify that it does not time out
Test: Hit 'done' on Guts - verifiy that it times out now
that guts are closed
Test: post hun, verify that it times out if not touched
Test: post hun, open guts, open shade - guts still shown
Test: post hun, open guts, open shade, close guts, close shade:
notification unpinned on shade open
Test: post hun, open guts, open shade, post new HUN: ordering
is correct; both unpinned on shade close
Fixes: 194024962

Change-Id: I3e46932e38e40355f2add60ffc90ec65506688c3