Fix undefined ansible_user_dir var in inject success flag task

#3036
Separate deployment from testing. As it also moves
`inject success flag` task to post-deployment playbook.

The play where `inject success flag` task runs, gather_facts
is set to false. ansible_user_dir is coming undefined.

In order to fix that, we are adding a task to collect
ansible_user_dir fact. This will make sure ansible_user_dir
exists.

Note: This code is generated by Gemini 2.5 Flash with following
prompt
```
what gather_facts I can run to collect ansible_user_dir
```

Generated-By: Gemini 2.5 Flash
Signed-off-by: Chandan Kumar (raukadah) <raukadah@gmail.com>

Author: raukadah

post-deployment.yml

@@ -54,6 +54,12 @@
       ansible.builtin.import_role:
         name: run_hook
 
+    - name: Gather minimal facts for ansible_user_dir
+      ansible.builtin.setup:
+        gather_subset:
+          - min
+        filter: "ansible_user_dir"
+
     - name: Inject success flag
       ansible.builtin.file:
         path: "{{ ansible_user_dir }}/cifmw-success"