### 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
if self.shell is not None and info[6] != self.shell:
            cmd.append('-s')
            cmd.append(self.shell)
        if self.login_class is not None:
            
            user_login_class = None
            userinfo_cmd = [self.module.get_bin_path('userinfo', True), self.name]
            (rc, out, err) = self.execute_command(userinfo_cmd, obey_checkmode=False)
            for line in out.splitlines():
                tokens = line.split()
                if tokens[0] == 'class' and len(tokens) == 2:
                    user_login_class = tokens[1]
            
            if self.login_class != user_login_class:
                cmd.append('-L')
                cmd.append(self.login_class)
        if self.password_lock and not info[1].startswith('*'):
            cmd.append('-Z')
        elif self.password_lock is False and info[1].startswith('*'):
            cmd.append('-U')
        if self.update_password == 'always' and self.password is not None \
                and self.password != '*' and info[1] != self.password:
            cmd.append('-p')
            cmd.append(self.password)
        
        if len(cmd) == 1:
            return (None, '', '')
        cmd.append(self.name)
        return self.execute_command(cmd)
class NetBSDUser(User):