Re-align packer templates with upstream

common-packer co-opted a variable that was in use in local templates and
therefore is causing verification errors when the matrix validate
happens.

Change-Id: Ia0232836ddcda114409b2fc71705c5c4e97d90a0
Signed-off-by: Andrew Grimberg <agrimberg@linuxfoundation.org>
diff --git a/packer/templates/baseline.json b/packer/templates/baseline.json
index 532e15a..3972d54 100644
--- a/packer/templates/baseline.json
+++ b/packer/templates/baseline.json
@@ -6,7 +6,6 @@
     "source_ami_filter_name": null,
     "source_ami_filter_owner": null,
     "subnet_id": null,
-    "cloud_user": null,
     "distro": null,
     "cloud_user_data": null
   },
@@ -27,7 +26,7 @@
         "most_recent": true,
         "owners": ["{{user `source_ami_filter_owner`}}"]
       },
-      "ssh_username": "{{user `cloud_user`}}",
+      "ssh_username": "{{user `ssh_user`}}",
       "subnet_id": "{{user `subnet_id`}}",
       "type": "amazon-ebs",
       "user_data_file": "{{user `cloud_user_data`}}"