[logout-greeter] Fix shutdown

In porting from kdelibs4support slotHalt got missed.

logout-greeter/shutdowndlg.cpp

@@ -300,7 +300,7 @@ void KSMShutdownDlg::slotLockScreen()
 void KSMShutdownDlg::slotHalt()
 {
     m_bootOption.clear();
-    m_shutdownType = KWorkSpace::ShutdownTypeHalt;
+    m_session.requestShutdown(SessionManagement::ConfirmationMode::Skip);
     accept();
 }
 

logout-greeter/shutdowndlg.h

@@ -69,7 +69,6 @@ protected:
 
 private:
     void setupWaylandIntegration();
-    KWorkSpace::ShutdownType m_shutdownType;
     QString m_bootOption;
     QStringList rebootOptions;
     bool m_result : 1;