Otherwise all code that calls it has to handle the other connections
separately, which is error-prone and has actually been forgotten for the
case where the QWebSocket is created via upgradeFrom().

Task-number: QTBUG-39551
Change-Id: I4d1e4faa1594b53e7a8dccc9ce13ef2c323b1c61
Reviewed-by: Kurt Pattyn <pattyn.kurt@gmail.com>