Added guest-desktop-agents to Server variant

variants.xml

@@ -208,6 +208,7 @@
       <group default="false">ftp-server</group>
       <group default="false">gnome-desktop</group>
       <group default="false">guest-agents</group>
+      <group default="false">guest-desktop-agents</group>
       <group default="false">hardware-monitoring</group>
       <group default="false">hardware-support</group>
       <group default="false">headless-management</group>