##### SUMMARY

The merge of #45507 broke `update_password="on_create"` on Alpine Linux with the shadow package installed.

This does not work anymore
```yml
  - name: add users                                                                                                                                                                                                                                  
    user:
      name: "{{ item.name }}"
      comment: "{ item.comment }}"
      shell: "/bin/zsh"
      password: '*'
      update_password: on_create
   with_items:
    ....
```

After the PR, all users that have a password that is not '*' will get their password changed.

Reverting bf3e397ea7922e8bd8b8ffbc05d1aede0317d119, makes 'update_password: on_create' work as expected again.

##### ISSUE TYPE
- Bug Report

##### COMPONENT NAME
<!--- Write the short name of the module, plugin, task or feature below, use your best guess if unsure -->

lib/ansible/modules/system/user.py

##### ANSIBLE VERSION
<!--- Paste verbatim output from "ansible --version" between quotes -->
```paste below
2.8.7
```

##### CONFIGURATION
<!--- Paste verbatim output from "ansible-config dump --only-changed" between quotes -->
```paste below

```

##### OS / ENVIRONMENT
<!--- Provide all relevant information below, e.g. target OS versions, network device firmware, etc. -->

Alpine Linux

##### STEPS TO REPRODUCE
<!--- Describe exactly how to reproduce the problem, using a minimal test-case -->

<!--- Paste example playbooks or commands between quotes below -->
```yaml
  - name: add users                                                                                                                                                                                                                                  
    user:
      name: "{{ item.name }}"
      comment: "{ item.comment }}"
      shell: "/bin/zsh"
      password: '*'
      update_password: on_create
```

<!--- HINT: You can paste gist.github.com links for larger files -->

##### EXPECTED RESULTS
<!--- Describe what you expected to happen when running the steps above -->

Users that are not created does not get their password changed.

##### ACTUAL RESULTS
<!--- Describe what actually happened. If possible run with extra verbosity (-vvvv) -->

<!--- Paste verbatim command output between quotes -->
```paste below
Password "hash" changed to '*'
```

description:
            - C(always) will update passwords if they differ.
            - C(on_create) will only set the password for newly created users.
        type: str
        choices: [ always, on_create ]
        default: always
        version_added: "1.3"
    expires:
        description:
            - An expiry time for the user in epoch, it will be ignored on platforms that do not support this.
            - Currently supported on GNU/Linux, FreeBSD, and DragonFlyBSD.
            - Since Ansible 2.6 you can remove the expiry time specify a negative value.
              Currently supported on GNU/Linux and FreeBSD.
        type: float
        version_added: "1.9"
    password_lock:
        description:
            - Lock the password (usermod -L, pw lock, usermod -C).
            - BUT implementation differs on different platforms, this option does not always mean the user cannot login via other methods.
            - This option does not disable the user, only lock the password. Do not change the password in the same task.
            - Currently supported on Linux, FreeBSD, DragonFlyBSD, NetBSD, OpenBSD.
        type: bool
        version_added: "2.6"
    local:
        description:
            - Forces the use of "local" command alternatives on platforms that implement it.
            - This is useful in environments that use centralized authentification when you want to manipulate the local users
              (i.e. it uses C(luseradd) instead of C(useradd)).
            - This will check C(/etc/passwd) for an existing account before invoking commands. If the local account database
              exists somewhere other than C(/etc/passwd), this setting will not work properly.