[applets/notifications] Be more lenient WRT when to show the clear action
requested to merge ngraham/plasma-workspace:be-more-liberal-showing-clear-notifications-action into master
Right now the "clear all" action only shows itself when there are any expired notifications. Because this count can differ from the number of total notifications shown, there can sometimes arise situations in which notifications are visible in the applet but the "clear all" action is not visible. Let's fix this by letting the action be visible whenever there are any notifications at all visible in the applet.
cc @broulik