gen_hosts: Add missing generic workflow template

When no specific workflow is configured in kdevops (CONFIG_WORKFLOWS=y
but no specific workflow like fstests, blktests, etc. selected), the
gen_hosts role would fail with:

  Error rendering template: 'workflows/generic.j2' not found

This occurs because the hosts.j2 template tries to include
'workflows/generic.j2' when kdevops_workflow_name is undefined, but
this template file didn't exist.

The solution adds a new generic.j2 template that handles the case where
no specific workflow is configured. It creates a simple hosts inventory
using the kdevops_host_prefix as the node name.

The template also properly handles the case where all_generic_nodes
might not be defined, which can happen with certain cloud providers
like Lambda Labs when using Terraform without a dedicated workflow.

This fix allows users to:
- Use kdevops with cloud providers without selecting a specific workflow
- Get started with basic infrastructure provisioning before choosing a
  testing workflow
- Avoid build failures during initial configuration

Fixes: 40df5ef ("gen_hosts: use kdevops_workflow_name directly for template selection")
Generated-by: Claude AI
Signed-off-by: Luis Chamberlain <[email protected]>

Author: mcgrof

playbooks/roles/gen_hosts/templates/hosts.j2

@@ -8,7 +8,10 @@ its own jinja2 template file and define its own ansible task for its generation.
 {% if kdevops_declared_hosts is defined and kdevops_declared_hosts %}
 {# Use declared hosts that skip bringup process - for bare metal or pre-existing infrastructure #}
 {% include 'workflows/declared-hosts.j2' %}
-{% else %}
+{% elif kdevops_workflow_name is defined and kdevops_workflow_name %}
 {# Include workflow-specific template dynamically based on workflow name #}
 {% include 'workflows/' + kdevops_workflow_name + '.j2' %}
+{% else %}
+{# No workflow defined - use generic template #}
+{% include 'workflows/generic.j2' %}
 {% endif %}

playbooks/roles/gen_hosts/templates/workflows/generic.j2

@@ -0,0 +1,22 @@
+{# Generic hosts template for when no specific workflow is configured #}
+{% if all_generic_nodes is defined %}
+{% set nodes = all_generic_nodes %}
+{% else %}
+{# Default to using the host prefix as the node name #}
+{% set nodes = [kdevops_host_prefix] %}
+{% endif %}
+[all]
+{% for node in nodes %}
+{{ node }}
+{% endfor %}
+
+[all:vars]
+ansible_python_interpreter = "{{ kdevops_python_interpreter }}"
+
+[{{ kdevops_host_prefix | regex_replace('-$', '') }}]
+{% for node in nodes %}
+{{ node }}
+{% endfor %}
+
+[{{ kdevops_host_prefix | regex_replace('-$', '') }}:vars]
+ansible_python_interpreter = "{{ kdevops_python_interpreter }}"