Fix empty sslConfiguration in sslErrors slot

If QWebSocket fires signal sslErrors the
QSslConfiguration of QWebSocket is not updated.
So client application cannot check it in
implemented slot.

Fix this by calling the update method like
for encrypted signal.

Sibling of QTBUG-40401.

Change-Id: I18b39f6b6a0791ae67fc2bff5cf2c04a22b0ab85
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>
Reviewed-by: Timur Pocheptsov <timur.pocheptsov@qt.io>