### 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
name:
        description:
            - Name of the user to create, remove or modify.
        type: str
        required: true
        aliases: [ user ]
    uid:
        description:
            - Optionally sets the I(UID) of the user.
        type: int
    comment:
        description:
            - Optionally sets the description (aka I(GECOS)) of user account.
        type: str
    hidden:
        description:
            - macOS only, optionally hide the user from the login window and system preferences.
            - The default will be C(yes) if the I(system) option is used.
        type: bool
        version_added: "2.6"
    non_unique:
        description:
            - Optionally when used with the -u option, this option allows to change the user ID to a non-unique value.
        type: bool
        default: no
        version_added: "1.1"
    seuser:
        description:
            - Optionally sets the seuser type (user_u) on selinux enabled systems.
        type: str