tst_QTcpSocket: fix disconnectWhileLookingUp

... and unblacklist it on Windows.

From what I can tell there is no particular reason why this test fails
other than that it is a little too slow sometimes (these things happen).

So, to fix the test I bumped the timeout, but to avoid the test running
for longer on every test-run it now also ends when the socket enters
the "Unconnected" state.

Previously it failed 171/500 times, and after this patch it failed
0/1000 times.

Change-Id: I4266bff6b91aaaf502ee66265d01c3a177706402
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Jesus Fernandez <Jesus.Fernandez@qt.io>

tests/auto/network/socket/qtcpsocket/BLACKLIST

@@ -6,8 +6,6 @@ windows
 windows
 [invalidProxy:socks5-on-http]
 windows
-[disconnectWhileLookingUp]
-windows
 [timeoutConnect:ip]
 windows
 ]

tests/auto/network/socket/qtcpsocket/tst_qtcpsocket.cpp

@@ -1447,8 +1447,15 @@ void tst_QTcpSocket::disconnectWhileLookingUp()
     }
 
     // let anything queued happen
+
     QEventLoop loop;
-    QTimer::singleShot(50, &loop, SLOT(quit()));
+    // If 'doClose' is false then we called '::waitForDisconnected' earlier, meaning
+    // we are already 'Unconnected'. So we don't need to wait for any potentially slow host lookups.
+    QTimer::singleShot(doClose ? 4000 : 50, &loop, SLOT(quit()));
+    connect(socket, &QTcpSocket::stateChanged, [&loop](QAbstractSocket::SocketState state) {
+        if (state == QAbstractSocket::UnconnectedState)
+            loop.exit(); // we don't need to wait for the timer to expire; we're done.
+    });
     loop.exec();
 
     // recheck