use HPC image for the Headnode

examples/beegfs_data_disk/config.json

@@ -30,7 +30,7 @@
             "vm_type": "Standard_D8s_v3",
             "accelerated_networking": true,
             "public_ip": true,
-            "image": "variables.image",
+            "image": "variables.hpc_image",
             "subnet": "compute",
             "data_disks": [2048, 2048],
             "tags": [