BlackBerry 10: make DNS traffic use bound socket instead of default interface

https://codereview.qt-project.org/49682 fixes binding to a socket, which is also used on the HTTP layer when a specific network configuration is set on a QNetworkAccessManager instance.
The problem with this is that DNS traffic will always go over the default interface; however on BlackBerry, there is an option to specify which device should be used for DNS traffic.