Fix default images

Author: arnaudfroidmont

schema.yaml

@@ -422,7 +422,7 @@ variables:
       - "GPU_OL7_NV550"
       - "GPU_OL8_NV535"
       - "GPU_OL7_NV535"
-    default: "GPU_OL8_NV550"
+    default: "HPC_OL8"
     visible: ${use_marketplace_image_controller}
 
   controller_username: 
@@ -766,7 +766,7 @@ variables:
       - "GPU_OL7_NV550"
       - "GPU_OL8_NV535"
       - "GPU_OL7_NV535"
-    default: "HPC_OL8"
+    default: "GPU_OL8_NV550"
     visible: ${use_marketplace_image}
 
   use_compute_agent: