tests: use contains(QT_CONFIG,private_tests) consistently

These tests used requires(contains(QT_CONFIG,private_tests)) in their
.pro file, but did not subtract themselves from their parent project
SUBDIRS when private_tests weren't enabled.

In the best case, this wastes a little time as qmake iterates over these
projects which won't be built.  In some worse esoteric cases, this may
break compilation or packaging.

Change-Id: I189c108ee9943b15114becf9d6b04f78dbabbe31
Reviewed-on: http://codereview.qt-project.org/4389
Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Toby Tomkins <toby.tomkins@nokia.com>

tests/auto/dbus.pro

@@ -18,3 +18,6 @@ SUBDIRS=\
            qdbusthreading \
            qdbusxmlparser \
 
+!contains(QT_CONFIG,private_tests): SUBDIRS -= \
+           qdbusmarshall \
+

tests/auto/gui.pro

@@ -218,11 +218,11 @@ win32:SUBDIRS -= qtextpiecetable
            qgraphicssceneindex \
            qlistwidget \
            qmainwindow \
-           qnetworkreply \
            qpathclipper \
            qpixmapcache \
            qsidebar \
            qstylesheetstyle \
+           qtcpsocket \
            qtextlayout \
            qtextpiecetable \
            qtipc \

tests/auto/network.pro

@@ -51,6 +51,10 @@ SUBDIRS=\
     qhttpnetworkconnection \
     qhttpnetworkreply \
     qhttpsocketengine \
+    qnetworkreply \
     qsocketnotifier \
     qsocks5socketengine \
+    qsslsocket \
+    qsslsocket_onDemandCertificates_member \
+    qsslsocket_onDemandCertificates_static \