False negatives solution

`is_event_assigned` was giving false negatives. This resolves this issue by adding `move_to_element`, because `is_displayed` returns `False` even when the element is displayed, but off screen. @seandst, @weissjeffm, @psav, we might like to add `move_to_element` also to `is_displayed`.

`is_displayed` is now removed in this part of code as we already check for `NoSuchElementException`