QNetworkAccessManager: delete the httpThread

QNetworkAccessManager: delete the httpThread

The httpThread was using deleteLater the finished signal of the
thread to call the deleteLater slot. If the QNetworkAccessManager is
deleted when the application is closed then then fished is emitted
but we never return to the eventloop so the deletion is never done.

This will delete the httpThread directly instead of using deleteLater

Task-number: QTBUG-25487
Change-Id: I1fdbd4eca01e8bd8b3a98936298e5c78217752b4
Reviewed-by: Shane Kearns <shane.kearns@accenture.com>