Keyboard: avoid multiple connects

When selecting keyboard layout, pause, then select another, the
QTimer wasn't being disconnected from the previously selected
language, so the second selection would fire the timeout, and
then call *two* slots .. and then three, ... Disconnect when
the timer fires, too.

src/modules/keyboard/KeyboardPage.cpp

@@ -323,6 +323,7 @@ KeyboardPage::onListVariantCurrentItemChanged( QListWidgetItem* current, QListWi
         QProcess::execute( QString( "setxkbmap -layout \"%1\" -variant \"%2\"" )
                            .arg( layout, variant ).toUtf8() );
         cDebug() << "xkbmap selection changed to: " << layout << "-" << variant;
+        m_setxkbmapTimer.disconnect( this );
     } );
     m_setxkbmapTimer.start( QApplication::keyboardInputInterval() );