Replace KDBusService usage with QDBusConnection when D-Bus activated

This is lighter and more reliable when it comes to being activated by
KUnifiedPush. We also don't need all of the features of KDBusService
here.

(cherry picked from commit 960377838d)

src/app/main.cpp

@@ -219,8 +219,14 @@ int main(int argc, char *argv[])
 
 #ifdef HAVE_KUNIFIEDPUSH
     if (parser.isSet(dbusActivatedOption)) {
-        // We want to be replaceable by the main client
-        KDBusService service(KDBusService::Replace);
+#ifdef HAVE_KDBUSADDONS
+        // We *don't* want to use KDBusService here. I don't know why, but it makes activation super unreliable. We don't really need it anyway.
+        if (!QDBusConnection::sessionBus().registerService(QStringLiteral("org.kde.neochat"))) {
+            // Gracefully fail if NeoChat is already running
+            qWarning() << "NeoChat already running, not sending push notifications.";
+            return 0;
+        }
+#endif
 
 #ifdef HAVE_RUNNER
         // If we are built with KRunner and KUnifiedPush support, we need to do something special.