Stabilize tst_signatureTest

Make sure clients get their slot invocations ACK'd before shutting down
the server

Change-Id: I24ed944cad0af2e4af936cd746523f222e48cb89
Reviewed-by: Continuous Integration (KDAB) <build@kdab.com>
Reviewed-by: Brett Stottlemyer <bstottle@ford.com>

tests/auto/repc/signature/signatureServer/main.cpp

@@ -60,6 +60,8 @@ public slots:
 
     bool quit() Q_DECL_OVERRIDE
     {
+        qDebug() << "quit() called";
+
         return shouldQuit = true;
     }
 };
@@ -79,6 +81,9 @@ private Q_SLOTS:
         qDebug() << "Waiting for incoming connections";
 
         QTRY_VERIFY_WITH_TIMEOUT(myTestServer.shouldQuit, 20000); // wait up to 20s
+
+        qDebug() << "Stopping server";
+        QTest::qWait(200); // wait for server to send reply to client invoking quit() function
     }
 };