qt: Stop shutdown detection timer during shutdown

Stop the shutdown timer from exiting the main loop
when shutdown is already in progress.

Fixes seeming hanging window after typing 'stop' in debug console.

Also hide the debug console during shutdown as it is useless without
a core to connect to.

src/qt/bitcoingui.cpp

@@ -855,7 +855,11 @@ void BitcoinGUI::toggleHidden()
 void BitcoinGUI::detectShutdown()
 {
     if (ShutdownRequested())
-        QMetaObject::invokeMethod(QCoreApplication::instance(), "quit", Qt::QueuedConnection);
+    {
+        if(rpcConsole)
+            rpcConsole->hide();
+        qApp->quit();
+    }
 }
 
 static bool ThreadSafeMessageBox(BitcoinGUI *gui, const std::string& message, const std::string& caption, unsigned int style)