Fix failing focus tests

jQuery 1.9 changes how $.focus() calls are handled: instead of
directly calling the handlers, it just invokes the DOM element's
focus(), and leaves it to the browser's event handling to trigger
them. This can fail for several reasons (e.g. element is not
attached to document, element is already focused, browser bugs such
as http://bugs.jquery.com/ticket/13363 ), so we are using
triggerHandler('focus') instead, which calls the handlers directly
without simulating actual browser events. Since these are unit
tests verifying event handler attach/unattach behavior, not
acceptance tests verifying actual event handling behavior, that
should be okay.

Change-Id: I65ecda28ace4f380ad33d6212e12069e18001232