### 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
chunk = os.read(master_out_fd, 10240)
                            out_buffer += chunk
                            if prompt in out_buffer:
                                os.write(master_in_fd, to_bytes(self.ssh_passphrase, errors='strict') + b'\r')
                                prompt = second_prompt
                        else:
                            chunk = os.read(master_err_fd, 10240)
                            err_buffer += chunk
                            if prompt in err_buffer:
                                os.write(master_in_fd, to_bytes(self.ssh_passphrase, errors='strict') + b'\r')
                                prompt = second_prompt
                        if b'Overwrite (y/n)?' in out_buffer or b'Overwrite (y/n)?' in err_buffer:
                            
                            return (None, 'Key already exists', '')
                rc = p.returncode
                out = to_native(out_buffer)
                err = to_native(err_buffer)
            except OSError as e:
                return (1, '', to_native(e))
        else:
            cmd.append('-N')
            cmd.append('')
            (rc, out, err) = self.execute_command(cmd, data=overwrite)
        if rc == 0 and not self.module.check_mode:
            
            
            os.chown(ssh_key_file, info[2], info[3])
            os.chown('%s.pub' % ssh_key_file, info[2], info[3])
        return (rc, out, err)
    def ssh_key_fingerprint(self):