Fixes swipe gesture on non-dismissable notifications.

This change modifies the condition under which NotificationSwipeHelper
decides to snap a notification to the "menu open" state after a gesture
such that a gesture on a non-dismissable notification which would be
fast enough to dismiss it opens the menu.

Test: manually
Change-Id: Ibbe3f1fc20d5990fb3dbc2c9edfe7599a880f65f