### Summary

When using the user module to modify password_expire_min=0, the processing result does not meet expectations .
I guess the problem is caused by the following code in the user module.
```
    # deal with password expire min
    if user.password_expire_min:
        if user.user_exists():
            (rc, out, err) = user.set_password_expire_min()
```
Modifying to the following  code may fix this problem.
```
    # deal with password expire min
    if user.password_expire_min is not None:
        if user.user_exists():
            (rc, out, err) = user.set_password_expire_min()
```

### Issue Type

Bug Report

### Component Name

user

### Ansible Version

```console
$ ansible --version
ansible [core 2.11.1] 
  config file = None
  configured module search path = ['/home/betadmin/.ansible/plugins/modules', '/usr/share/ansible/plugins/modules']
  ansible python module location = /app/python3/lib/python3.8/site-packages/ansible
  ansible collection location = /home/betadmin/.ansible/collections:/usr/share/ansible/collections
  executable location = /app/python3/bin/ansible
  python version = 3.8.5 (default, Sep 18 2020, 14:55:53) [GCC 4.8.5 20150623 (Red Hat 4.8.5-16)]
  jinja version = 2.11.2
  libyaml = False
```


### Configuration

```console
$ ansible-config dump --only-changed
```


### OS / Environment

RHEL 7.4

### Steps to Reproduce

- name: Edit password_expire_min
  user:
    name: test
    password_expire_min: 0



### Expected Results

Minimum number of days between password change	: 0


### Actual Results


Minimum number of days between password change	: 2


### Code of Conduct

- [X] I agree to follow the Ansible Code of Conduct
- Currently supported on Linux.
            - Requires C(local) is omitted or False.
        type: str
        version_added: "2.12"
extends_documentation_fragment: action_common_attributes
attributes:
    check_mode:
        support: full
    diff_mode:
        support: none
    platform:
        platforms: posix
notes:
  - There are specific requirements per platform on user management utilities. However
    they generally come pre-installed with the system and Ansible will require they
    are present at runtime. If they are not, a descriptive error message will be shown.
  - On SunOS platforms, the shadow file is backed up automatically since this module edits it directly.
    On other platforms, the shadow file is backed up by the underlying tools used by this module.
  - On macOS, this module uses C(dscl) to create, modify, and delete accounts. C(dseditgroup) is used to
    modify group membership. Accounts are hidden from the login window by modifying
    C(/Library/Preferences/com.apple.loginwindow.plist).
  - On FreeBSD, this module uses C(pw useradd) and C(chpass) to create, C(pw usermod) and C(chpass) to modify,
    C(pw userdel) remove, C(pw lock) to lock, and C(pw unlock) to unlock accounts.
  - On all other platforms, this module uses C(useradd) to create, C(usermod) to modify, and
    C(userdel) to remove accounts.
seealso:
- module: ansible.posix.authorized_key
- module: ansible.builtin.group
- module: ansible.windows.win_user
author: