### 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?

try:
            try:
                f = open(self.HOSTNAME_FILE, 'r')
                lines = [x.strip() for x in f]
                for i, line in enumerate(lines):
                    if line.startswith('hostname='):
                        lines[i] = 'hostname="%s"' % name
                        break
                f.close()
                f = open(self.HOSTNAME_FILE, 'w')
                f.write('\n'.join(lines) + '\n')
            except Exception as e:
                self.module.fail_json(msg="failed to update hostname: %s" %
                                          to_native(e), exception=traceback.format_exc())
        finally:
            f.close()
class OpenBSDStrategy(GenericStrategy):
    """
    This is a OpenBSD family Hostname manipulation strategy class - it edits
    the /etc/myname file.
    """
    HOSTNAME_FILE = '/etc/myname'
    def get_permanent_hostname(self):