### SUMMARY 

[Flatcar Container Linux](https://www.flatcar-linux.org) is not properly discovered by Ansible, especially while setting hostname.

##### ISSUE TYPE
- Bug Report

##### COMPONENT NAME
hostname

##### ANSIBLE VERSION
```paste below
ansible --version
ansible 2.9.7
  config file = /etc/ansible/ansible.cfg
  configured module search path = ['.../.ansible/plugins/modules', '/usr/share/ansible/plugins/modules']
  ansible python module location = /usr/lib/python3.8/site-packages/ansible
  executable location = /usr/bin/ansible
  python version = 3.8.2 (default, Feb 28 2020, 00:00:00) [GCC 10.0.1 20200216 (Red Hat 10.0.1-0.8)]
```

##### OS / ENVIRONMENT
Guest OS: Flatcar Container Linux Alpha 2492.0.0
Host: Fedora 32

##### STEPS TO REPRODUCE
1. Clone [image builder](https://github.com/kubernetes-sigs/image-builder).
2. Adjust files for Flatcar.
3. Run `packer build`, which creates Flatcar image, provisions a host.

##### EXPECTED RESULTS
No error

##### ACTUAL RESULTS

Failure like:
```
flatcar-alpha: TASK [sysprep : Set hostname] **************************************************
    flatcar-alpha: fatal: [default]: FAILED! => {"changed": false, "msg": "hostname module cannot be  used on platform Linux (Flatcar)"}^
```

For info, in Flatcar you can see for example:
```
$ cat /etc/os-release 
NAME="Flatcar Container Linux by Kinvolk"
ID=flatcar
ID_LIKE=coreos
VERSION=2492.0.0
VERSION_ID=2492.0.0
BUILD_ID=2020-04-28-2210
PRETTY_NAME="Flatcar Container Linux by Kinvolk 2492.0.0 (Rhyolite)"
ANSI_COLOR="38;5;75"
HOME_URL="https://flatcar-linux.org/"
BUG_REPORT_URL="https://issues.flatcar-linux.org"
FLATCAR_BOARD="amd64-usr"

$ cat /etc/lsb-release 
DISTRIB_ID="Flatcar Container Linux by Kinvolk"
DISTRIB_RELEASE=2492.0.0
DISTRIB_CODENAME="Rhyolite"
DISTRIB_DESCRIPTION="Flatcar Container Linux by Kinvolk 2492.0.0 (Rhyolite)"
```

As far as I understand, so far Ansible only supported [CoreOS Container Linux](https://github.com/ansible/ansible/blob/cedfe34619128783d2a799695bd4c53d6adc9dd1/lib/ansible/module_utils/facts/system/distribution.py#L387), which will be soon EOL. Recently there was an attempt to support [Fedora CoreOS or RedHat CoreOS](https://github.com/ansible/ansible/pull/53563), which was not merged. I am not sure if there is any recent progress about that.

So would it be reasonable to simply add new code for Flatcar, just like CoreOS Container Linux?

smgl_facts = {}
        smgl_facts['distribution'] = 'Source Mage GNU/Linux'
        return smgl_facts
    def get_distribution_SunOS(self):
        sunos_facts = {}
        data = get_file_content('/etc/release').splitlines()[0]
        if 'Solaris' in data:
            
            uname_r = get_uname(self.module, flags=['-r'])
            ora_prefix = ''
            if 'Oracle Solaris' in data:
                data = data.replace('Oracle ', '')
                ora_prefix = 'Oracle '
            sunos_facts['distribution'] = data.split()[0]
            sunos_facts['distribution_version'] = data.split()[1]
            sunos_facts['distribution_release'] = ora_prefix + data
            sunos_facts['distribution_major_version'] = uname_r.split('.')[1].rstrip()
            return sunos_facts
        uname_v = get_uname(self.module, flags=['-v'])
        distribution_version = None
        if 'SmartOS' in data:
            sunos_facts['distribution'] = 'SmartOS'
            if _file_exists('/etc/product'):
                product_data = dict([l.split(': ', 1) for l in get_file_content('/etc/product').splitlines() if ': ' in l])
                if 'Image' in product_data:
                    distribution_version = product_data.get('Image').split()[-1]
        elif 'OpenIndiana' in data: