Understand file:/ url's as local

When making a QNetworkAccessManager query, don't require a network
session in case of file:/ queries, like we do when "localhost" is the
hostname or a loopback device.

Change-Id: I4faab7cf356ee53e6e13ab55b152365680af9446
Reviewed-by: Albert Astals Cid <albert.astals@canonical.com>
Reviewed-by: Richard J. Moore <rich@kde.org>

src/network/access/qnetworkaccessbackend.cpp

@@ -383,7 +383,8 @@ bool QNetworkAccessBackend::start()
             const QString host = reply->url.host();
 
             if (host == QLatin1String("localhost") ||
-                QHostAddress(host).isLoopback()) {
+                QHostAddress(host).isLoopback() ||
+                reply->url.isLocalFile()) {
                 // Don't need an open session for localhost access.
             } else {
                 // need to wait for session to be opened