Fix default(omit) placeholder leak in install-config template

OSPRH-6485

Co-authored-by: Cursor <cursoragent@cursor.com>

Author: tusharjadhav3302

collection/stages/roles/install/tasks/install_config_generation/ipi_install_config.yml

@@ -45,9 +45,9 @@
     installcfg_api_vips: "{{ ocp_deployment_topology.primary_ip_protocol == 'ipv6' }}"
     installcfg_api_floating_ip: "{{ precreated_api_fip }}"
     installcfg_ingress_floating_ip: "{{ precreated_ingress_fip }}"
-    installcfg_machines_subnet: "{{ machines_subnet_id | default(omit) }}"
+    installcfg_machines_subnet: "{{ machines_subnet_id | default('') }}"
     installcfg_cluster_network: "{{ ocp_deployment_topology[ocp_deployment_topology.primary_ip_protocol].cluster_network }}"
     installcfg_service_network: "{{ ocp_deployment_topology[ocp_deployment_topology.primary_ip_protocol].service_network }}"
     installcfg_default_machine_platform: "{{ ocp_deployment_topology.defaultMachinePlatform | default({}) }}"
     installcfg_cluster_os_image_properties: "{{ ocp_deployment_topology.platform.openstack.clusterOSImageProperties | default({}) }}"
-    installcfg_additional_trust_bundle: "{{ _cacert_content.stdout_lines | default(omit) }}"
+    installcfg_additional_trust_bundle: "{{ _cacert_content.stdout_lines | default([]) }}"

collection/stages/roles/install/templates/install-config-ipi.yaml.j2

@@ -45,7 +45,7 @@ platform:
       {{ key }}: {{ value }}
       {%- endfor +%}
     {%- endif +%}
-    {%- if installcfg_machines_subnet is defined +%}
+    {%- if installcfg_machines_subnet +%}
     machinesSubnet: {{ installcfg_machines_subnet }}
     {%- endif +%}
     {%- if installcfg_api_vips +%}
@@ -64,15 +64,15 @@ platform:
     externalNetwork:  "{{ installcfg_external_network }}"
     apiFloatingIP:     "{{ installcfg_api_floating_ip }}"
     ingressFloatingIP: "{{ installcfg_ingress_floating_ip }}"
-    {%- if installcfg_machines_subnet is not defined +%}
+    {%- if not installcfg_machines_subnet +%}
     externalDNS: {{ installcfg_dns_servers }}
     {%- endif +%}
     {%- endif +%}
 pullSecret: |
   {{ ocp_pull_secret }}
 sshKey: |
   {{ ocp_public_key }}
-{%- if installcfg_additional_trust_bundle is defined +%}
+{%- if installcfg_additional_trust_bundle +%}
 additionalTrustBundle: |
 {% for line in installcfg_additional_trust_bundle %}
   {{ line }}