Skip unstable autotests in QtBase.

The combination of these unstable tests makes it very
hard to get changes through the CI system due to the
unrelated test failures.

Skip the following test functions:
tst_QIODevice::unget QTBUG-39983 (Mac)
tst_QThreadPool:expiryTimeoutRace QTBUG-3786 (Windows)
tst_QLocalSocket::processConnection QTBUG-39986 (Mac)
tst_QTcpServer::adressReusable QTBUG-39985 (Linux)

Change-Id: I96559bea0d437fd25966b6ccac1ece1490e06241
Reviewed-by: David Faure <david.faure@kdab.com>
Reviewed-by: Shawn Rutledge <shawn.rutledge@digia.com>

tests/auto/corelib/io/qiodevice/tst_qiodevice.cpp

@@ -193,6 +193,9 @@ void tst_QIODevice::unget()
 {
 #if defined(Q_OS_WINCE) && defined(WINCE_EMULATOR_TEST)
     QSKIP("Networking tests in a WinCE emulator are unstable");
+#endif
+#if defined(Q_OS_MAC)
+    QSKIP("The unget network test is unstable on Mac. See QTBUG-39983.");
 #endif
     QBuffer buffer;
     buffer.open(QBuffer::ReadWrite);

tests/auto/corelib/thread/qthreadpool/tst_qthreadpool.cpp

@@ -371,6 +371,9 @@ void tst_QThreadPool::expiryTimeout()
 
 void tst_QThreadPool::expiryTimeoutRace() // QTBUG-3786
 {
+#ifdef Q_OS_WIN
+    QSKIP("This test is unstable on Windows. See QTBUG-3786.");
+#endif
     ExpiryTimeoutTask task;
 
     QThreadPool threadPool;

tests/auto/network/socket/qlocalsocket/tst_qlocalsocket.cpp

@@ -829,6 +829,10 @@ private:
  */
 void tst_QLocalSocket::processConnection()
 {
+#ifdef Q_OS_MAC
+    QSKIP("The processConnection test is unstable on Mac. See QTBUG-39986.");
+#endif
+
 #ifdef Q_OS_WIN
     const QString exeSuffix = QStringLiteral(".exe");
 #else

tests/auto/network/socket/qtcpserver/tst_qtcpserver.cpp

@@ -576,6 +576,9 @@ protected:
 #ifndef QT_NO_PROCESS
 void tst_QTcpServer::addressReusable()
 {
+#ifdef Q_OS_LINUX
+    QSKIP("The addressReusable test is unstable on Linux. See QTBUG-39985.");
+#endif
     QFETCH_GLOBAL(bool, setProxy);
     if (setProxy) {
 #ifndef QT_NO_NETWORKPROXY