Fix Ansible 12 compatibility issues (closes #14838) (#14840)

This commit addresses three critical compatibility issues with Ansible 12:

1. **Nested Jinja template deprecation warning**
   - Fixed: `{{ lookup('file', '{{ SSH_keys.public }}') }}`
   - Now: `{{ lookup('file', SSH_keys.public) }}`
   - Location: files/cloud-init/base.sh:20

2. **String to boolean conversion errors in conditionals**
   - Fixed: `when: item.item` (evaluates strings as truthy)
   - Now: `when: item.item is defined and item.item != none`
   - Location: roles/common/tasks/main.yml:20

3. **Sysctl list with None values causing boolean errors**
   - Restructured list to dynamically exclude None entries
   - IPv6 forwarding sysctl only added when ipv6_support is true
   - Location: roles/common/tasks/ubuntu.yml:132

These changes maintain backward compatibility with older Ansible versions
while ensuring forward compatibility with Ansible 12's stricter type checking.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-authored-by: Claude <[email protected]>

Author: dguido

files/cloud-init/base.sh

@@ -17,7 +17,7 @@ cat <<EOF >/etc/ssh/sshd_config
 EOF
 
 test -d /home/algo/.ssh || sudo -u algo mkdir -m 0700 /home/algo/.ssh
-echo "{{ lookup('file', '{{ SSH_keys.public }}') }}" | (sudo -u algo tee /home/algo/.ssh/authorized_keys && chmod 0600 /home/algo/.ssh/authorized_keys)
+echo "{{ lookup('file', SSH_keys.public) }}" | (sudo -u algo tee /home/algo/.ssh/authorized_keys && chmod 0600 /home/algo/.ssh/authorized_keys)
 
 ufw --force reset
 

roles/common/tasks/main.yml

@@ -17,7 +17,7 @@
 
 - name: Sysctl tuning
   sysctl: name="{{ item.item }}" value="{{ item.value }}"
-  when: item.item
+  when: item.item is defined and item.item != none
   with_items:
     - "{{ sysctl | default([]) }}"
   tags:

roles/common/tasks/ubuntu.yml

@@ -129,15 +129,7 @@
       - openssl
       - gnupg2
       - cron
-    sysctl:
-      - item: net.ipv4.ip_forward
-        value: 1
-      - item: net.ipv4.conf.all.forwarding
-        value: 1
-      - item: "{{ 'net.ipv6.conf.all.forwarding' if ipv6_support else none }}"
-        value: 1
-      - item: net.ipv4.conf.all.route_localnet
-        value: 1
+    sysctl: "{{ [{'item': 'net.ipv4.ip_forward', 'value': 1}, {'item': 'net.ipv4.conf.all.forwarding', 'value': 1}, {'item': 'net.ipv4.conf.all.route_localnet', 'value': 1}] + ([{'item': 'net.ipv6.conf.all.forwarding', 'value': 1}] if ipv6_support else []) }}"
 
 - name: Install packages (batch optimization)
   include_tasks: packages.yml