### 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
cmd = self._get_dscl()
        cmd += ['-create', '/Users/%s' % self.name]
        (rc, out, err) = self.execute_command(cmd)
        if rc != 0:
            self.module.fail_json(msg='Cannot create user "%s".' % self.name, err=err, out=out, rc=rc)
        self._make_group_numerical()
        if self.uid is None:
            self.uid = str(self._get_next_uid(self.system))
        
        if self.create_home:
            if self.home is None:
                self.home = '/Users/%s' % self.name
            if not self.module.check_mode:
                if not os.path.exists(self.home):
                    os.makedirs(self.home)
                self.chown_homedir(int(self.uid), int(self.group), self.home)
        
        
        if not self.system and self.shell is None:
            self.shell = '/bin/bash'
        for field in self.fields:
            if field[0] in self.__dict__ and self.__dict__[field[0]]:
                cmd = self._get_dscl()
                cmd += ['-create', '/Users/%s' % self.name, field[1], self.__dict__[field[0]]]
                (rc, _out, _err) = self.execute_command(cmd)
                if rc != 0:
                    self.module.fail_json(msg='Cannot add property "%s" to user "%s".' % (field[0], self.name), err=err, out=out, rc=rc)
                out += _out
                err += _err
                if rc != 0: