### 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
self.module.fail_json(msg='Cannot user "%s" to hidden user list.' % self.name, err=err, out=out, rc=rc)
                return 0
        else:
            if self.name in hidden_users:
                del (hidden_users[hidden_users.index(self.name)])
                cmd = ['defaults', 'write', plist_file, 'HiddenUsersList', '-array'] + hidden_users
                (rc, out, err) = self.execute_command(cmd)
                if rc != 0:
                    self.module.fail_json(msg='Cannot remove user "%s" from hidden user list.' % self.name, err=err, out=out, rc=rc)
                return 0
    def user_exists(self):
        '''Check is SELF.NAME is a known user on the system.'''
        cmd = self._get_dscl()
        cmd += ['-read', '/Users/%s' % self.name, 'UniqueID']
        (rc, out, err) = self.execute_command(cmd, obey_checkmode=False)
        return rc == 0
    def remove_user(self):
        '''Delete SELF.NAME. If SELF.FORCE is true, remove its home directory.'''
        info = self.user_info()
        cmd = self._get_dscl()
        cmd += ['-delete', '/Users/%s' % self.name]
        (rc, out, err) = self.execute_command(cmd)
        if rc != 0:
            self.module.fail_json(msg='Cannot delete user "%s".' % self.name, err=err, out=out, rc=rc)
        if self.force:
            if os.path.exists(info[5]):
                shutil.rmtree(info[5])
                out += "Removed %s" % info[5]
        return (rc, out, err)
    def create_user(self, command_name='dscl'):