omyacid: try another tactic for default username

omyacid/templates/meta-data.yml

@@ -1,5 +1,5 @@
 instance_id: "iid-{{ inst_name }}"
-local_hostname: "{{ inst_name }}"
+local-hostname: "{{ inst_name }}"
 {% if !ssh_pubkeys.is_empty() -%}
 public-keys:
 {% for key in ssh_pubkeys -%}
@@ -7,5 +7,7 @@ public-keys:
 {% endfor %}
 {%- endif -%}
 {% if let Some(user) = username -%}
-default_username: "{{ user }}"
+system_info:
+  default_user:
+    name: "{{ user }}"
 {%- endif %}