Add variable for template filename

The current logic for constructing the template filename
does not allow custom scenario names. For example, if an
outside playbook defines ``boostrap_host_scenario`` to
be "swift" or "awesome_scenario", then the task would try
to look for the user_variables.swlft.yml.j2 template within the
role. This commit allows the user to define a template filename
using the variable bootstrap_user_variables_template.

Change-Id: I9fc98ea9b7d68623cb42c5fa3b9d5383fadb82d8

releasenotes/notes/add-template-file-var-cac35a99a3faf563.yaml

@@ -0,0 +1,6 @@
+---
+features:
+  - |
+    A variable named ``bootstrap_user_variables_template`` has been added
+    to the bootstrap-host role so the user can define the user variable
+    template filename for AIO deployments

tests/roles/bootstrap-host/defaults/main.yml

@@ -31,6 +31,9 @@ bootstrap_host_aio_script_path: "{{ playbook_dir }}/../scripts"
 bootstrap_host_user_variables_filename: "user_variables.yml"
 bootstrap_host_user_secrets_filename: "user_secrets.yml"
 
+# The user variables template to use
+bootstrap_user_variables_template: "user_variables.{{ bootstrap_host_scenario }}.yml.j2"
+
 ## Swap memory
 # If there is no swap memory present, the bootstrap will create a loopback disk
 # for the purpose of having swap memory available. Swap is required for some of

tests/roles/bootstrap-host/tasks/prepare_aio_config.yml

@@ -113,7 +113,7 @@
 
 - name: Set the user_variables
   config_template:
-    src: "user_variables.{{ bootstrap_host_scenario }}.yml.j2"
+    src: "{{ bootstrap_user_variables_template }}"
     dest: "/etc/openstack_deploy/{{ bootstrap_host_user_variables_filename }}"
     config_overrides: "{{ user_variables_overrides | default({}) }}"
     config_type: yaml