Use exists filter instead of stat where possible

When checking for the existance of a file on the host where
Ansible is being executed, using the stat module with localhost
delegation is rather heavy-handed. We can instead just make use
of the 'exists' test.

This should improve execution time just a little bit and reduces
the number of tasks for us to maintain. We also remove the
repetition of the task file path by using a variable.

Change-Id: I8b278ca83b2afb07575dbae2496ec265c3a06473

common/deploy-steps-tasks-step-0.j2.yaml

@@ -26,15 +26,10 @@
   copy: src=container_puppet_script.yaml dest=/var/lib/container-puppet/container-puppet.sh force=yes mode=0755 setype=container_file_t
 
 {%- for role in roles %}
-- name: Check for {{role.name}}/deploy_steps_tasks_step0.yaml
-  delegate_to: localhost
-  run_once: true
-  become: false
-  stat:
-    path: "{{ '{{' }} playbook_dir ~ '/' ~ '{{role.name}}' ~ '/' ~ 'deploy_steps_tasks_step0.yaml' {{ '}}' }}"
-  register: tasks_stat
-- include_tasks: {{role.name}}/deploy_steps_tasks_step0.yaml
+- include_tasks: "{% raw %}{{ _task_file_path }}{% endraw %}"
+  vars:
+    _task_file_path: "{{role.name}}/deploy_steps_tasks_step0.yaml"
   when:
     - tripleo_role_name == '{{role.name}}'
-    - tasks_stat.stat.exists
+    - "{% raw %}'{{ playbook_dir }}/{{ _task_file_path }}' is exists{% endraw %}"
 {%- endfor %}

common/deploy-steps.j2

@@ -709,17 +709,12 @@ outputs:
                   debug:
                     msg: Use --start-at-task 'Deploy step tasks for {{step}}' to resume from this task
 {%- for role in roles %}
-                - name: Check for {{role.name}}/deploy_steps_tasks_step{{step}}.yaml
-                  delegate_to: localhost
-                  become: false
-                  run_once: true
-                  stat:
-                    path: "{{ '{{' }} playbook_dir ~ '/' ~ '{{role.name}}' ~ '/' ~ 'deploy_steps_tasks_step{{step}}.yaml' {{ '}}' }}"
-                  register: tasks_stat
-                - include_tasks: {{role.name}}/deploy_steps_tasks_step{{step}}.yaml
+                - include_tasks: "{% raw %}{{ _task_file_path }}{% endraw %}"
+                  vars:
+                    _task_file_path: "{{role.name}}/deploy_steps_tasks_step{{step}}.yaml"
                   when:
                     - tripleo_role_name == '{{role.name}}'
-                    - tasks_stat.stat.exists
+                    - "{% raw %}'{{ playbook_dir }}/{{ _task_file_path }}' is exists{% endraw %}"
 {%- endfor %}
               tags:
                 - overcloud