Request headers are not yet handled, only the QNetworkRequest::url() is
taken into consideration.

[ChangeLog][QWebSocket] Added open(const QNetworkRequest &) and request()

Task-number: QTBUG-40842
Change-Id: Ia2e10f22c79b0a085afb9a2eb8437b7a73d4a045
Reviewed-by: Liang Qi <liang.qi@theqtcompany.com>