Options in data-setup attribute are ignored when the initialization is called before autoSetup

Because only `vjs.autoSetup` picks the option from `data-setup`, this attribute will be ignored if the initialization is called before that. Sometimes I face this issue and options in `data-setup` are ignored, so I made `Player.getTagSetting` pick the option from `data-setup` as well.
We should use our MakePlayer test helper here. It prevents executing the full player stack and can help avoid unrelated errors from happening.
https://github.com/videojs/video.js/blob/b65f2da65e848cd5a6e53debd295565de7e25067/test/unit/test-helpers.js#L8

You could do something like:
```
var el = PlayerTest.makeTag();
el.setAttribute('data-setup', '...');
var player = PlayerTest.makePlayer({}, el);
```