### 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
user.create_homedir(user.home)
                user.chown_homedir(info[2], info[3], user.home)
            result['changed'] = True
        
        if user.sshkeygen:
            
            (rc, out, err) = user.ssh_key_gen()
            if rc is not None and rc != 0:
                module.fail_json(name=user.name, msg=err, rc=rc)
            if rc == 0:
                result['changed'] = True
            (rc, out, err) = user.ssh_key_fingerprint()
            if rc == 0:
                result['ssh_fingerprint'] = out.strip()
            else:
                result['ssh_fingerprint'] = err.strip()
            result['ssh_key_file'] = user.get_ssh_key_path()
            result['ssh_public_key'] = user.get_ssh_public_key()
    
    if user.password_expire_max:
        if user.user_exists():
            user.set_password_expire_max()
    
    if user.password_expire_min:
        if user.user_exists():
            user.set_password_expire_min()
    module.exit_json(**result)
if __name__ == '__main__':
    main()