QNetworkReply may leak if host cannot be resolved

When performing several consequent HTTP request to a nonexistent host, only the first one will be finished and other requests will be leaked.

Steps to reproduce:
1. Send an HTTP request to a nonexistent host.
2. Connect to QNetworkReply::finished signal.
3. Repeat these steps two or more times in a row.

Expected Result:
QNetworkReply::finished signal is emitted for every request made.

Actual Result:
QNetworkReply::finished signal is emitted only for the first requests. All other QNetworkReply objects are leaked. If one more request is made after a certain delay, it will be leaked, while the first of previously leaked requests will be finished.

References:
1. test.zip - a sample that can be used to reproduce the bug.
2. fix_qnetworkreply_leak.patch - a patch that fixes the bug.