Switch integration test to mostly use unix sockets

By not using the same hardcoded number for every test, we can parallelize the test now.

There are several cases remaining where we can't easily use unix sockets (e.g. QSslSocket or imapauth module), for that ask kernel what port number is currently free to use. This is a bit racy though.

test/integration/framework/base.cpp

@@ -14,9 +14,12 @@
  * limitations under the License.
  */
 
-#include <gmock/gmock.h>
 #include "base.h"
 
+#include <gmock/gmock.h>
+
+#include <QTcpServer>
+
 using testing::AnyOf;
 using testing::Eq;
 
@@ -58,4 +61,10 @@ Process::~Process() {
     }
 }
 
+int PickPortNumber() {
+    QTcpServer tcp;
+    tcp.listen(QHostAddress::LocalHost);
+    return tcp.serverPort();
+}
+
 }  // namespace znc_inttest