Clean up kickstart post if else (#289)

* Clean up kickstart post is else

* Add fragment

* Fix lint

changelogs/fragments/289-clean-up-kickstart-post-if-else.yaml

@@ -0,0 +1,3 @@
+---
+minor_changes:
+  - Clean up kickstart post if else

roles/builder/vars/main.yml

@@ -14,6 +14,6 @@ builder_kickstart_options:
   - ostreesetup --nogpg --osname=rhel --remote=edge --url=http://{{ builder_system_ipv4 }}/{{ builder_blueprint_name }}/repo/ --ref={{ builder_blueprint_ref }}  # noqa yaml[line-length]
 _builder_kickstart_post:
   - "{{ lookup('ansible.builtin.template', '../templates/auto_register_aap.j2') if builder_aap_url is defined | default(None) }}"
-builder_kickstart_post: "{{ _builder_kickstart_post + additional_kickstart_post if additional_kickstart_post is defined else _builder_kickstart_post }}"
+builder_kickstart_post: "{{ _builder_kickstart_post + additional_kickstart_post if additional_kickstart_post is defined else (_builder_kickstart_post if _builder_kickstart_post is defined ) | default(None) }}"  # yamllint disable-line rule:line-length
 _builder_pub_key: "{{ builder_pub_key if builder_pub_key is defined else (builder_pub_key_path if builder_pub_key_path is defined else '') }}"
 _builder_compose_type: "{{ ('iot-commit' if ansible_distribution == 'Fedora' else 'edge-commit') if 'installer' in builder_compose_type or 'raw' in builder_compose_type else builder_compose_type }}"  # yamllint disable-line rule:line-length