fix/ansible-core 2.19: etcd: avoid mutating methods in template (#13474)

2.19 disallow methods with side effects in Jinja. Use a simple loop by
adding all the SANs source in one list.

Also check the sources before hand for failing on CIDR notation.

Link: https://github.com/ansible/ansible/issues/85202

roles/validate_inventory/meta/main.yml

@@ -1,3 +1,4 @@
 ---
 dependencies:
   - role: kubespray_defaults
+  - role: etcd_defaults