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: If36b1b8f69c3509128786fec67899ae18ffaa2bc
Reviewed-by: Toby Tomkins <toby.tomkins@nokia.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

tests/auto/network/socket/socket.pro

@@ -10,8 +10,7 @@ SUBDIRS=\
    platformsocketengine \
 
 !contains(QT_CONFIG, private_tests): SUBDIRS -= \
-          platformsocketengine \
-          qhttpsocketengine \
-          qsocks5socketengine \
-
-
+   platformsocketengine \
+   qtcpsocket \
+   qhttpsocketengine \
+   qsocks5socketengine \

tests/auto/network/ssl/ssl.pro

@@ -7,3 +7,8 @@ SUBDIRS=\
    qsslsocket \
    qsslsocket_onDemandCertificates_member \
    qsslsocket_onDemandCertificates_static \
+
+!contains(QT_CONFIG, private_tests): SUBDIRS -= \
+   qsslsocket \
+   qsslsocket_onDemandCertificates_member \
+   qsslsocket_onDemandCertificates_static \