Bug 1047168 - Modify test_play_youtube to play a video file locally

It is very weird to pass in `bool` here, we haven't used this style elsewhere in the suite at all.

If we're tapping play then I'd expect `is_playing` to be True. 

If you're tapping play and expecting it to pause then you're actually tapping the pause button.

Another way is to get the `is_playing` value first, then tap the button, then wait for `is_playing` to be different.