idempotence and no_log on "Execute create_user script" tasks

[Aohzan]

Hello,

I have two remarks about the Execute create_user script task:

1. As we provide a password, I think the task should have a no_log: true defined
2. A changed_when should be provide to specify when the script really changed something, if it's not possible to know that, changed_when: false can be the right solution

Thank you