### 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
new_cls = get_platform_subclass(User)
        return super(cls, new_cls).__new__(new_cls)
    def __init__(self, module):
        self.module = module
        self.state = module.params['state']
        self.name = module.params['name']
        self.uid = module.params['uid']
        self.hidden = module.params['hidden']
        self.non_unique = module.params['non_unique']
        self.seuser = module.params['seuser']
        self.group = module.params['group']
        self.comment = module.params['comment']
        self.shell = module.params['shell']
        self.password = module.params['password']
        self.force = module.params['force']
        self.remove = module.params['remove']
        self.create_home = module.params['create_home']
        self.move_home = module.params['move_home']
        self.skeleton = module.params['skeleton']
        self.system = module.params['system']
        self.login_class = module.params['login_class']
        self.append = module.params['append']
        self.sshkeygen = module.params['generate_ssh_key']
        self.ssh_bits = module.params['ssh_key_bits']
        self.ssh_type = module.params['ssh_key_type']
        self.ssh_comment = module.params['ssh_key_comment']
        self.ssh_passphrase = module.params['ssh_key_passphrase']
        self.update_password = module.params['update_password']