Don't always add controls to the video element

Fix for #1561. If the HTML tech is being constructed without a video element to work off of, make sure that the controls attribute is only added under the same circumstances it would be at player init. Before this fix, if you loaded the Flash tech and then switched to the HTML tech, you would see the native controls underneath the video.js controls.
I think we could get away with migrating all the controls-attribute manipulation into this function. I'll take a crack at it.