### 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?

platform = 'Linux'
    distribution = 'Opensuse-tumbleweed'
    strategy_class = SystemdStrategy
class AsteraHostname(Hostname):
    platform = 'Linux'
    distribution = '"astralinuxce"'
    strategy_class = SystemdStrategy
class ArchHostname(Hostname):
    platform = 'Linux'
    distribution = 'Arch'
    strategy_class = SystemdStrategy
class ArchARMHostname(Hostname):
    platform = 'Linux'
    distribution = 'Archarm'
    strategy_class = SystemdStrategy
class ManjaroHostname(Hostname):
    platform = 'Linux'
    distribution = 'Manjaro'
    strategy_class = SystemdStrategy
class RHELHostname(Hostname):
    platform = 'Linux'
    distribution = 'Redhat'
    strategy_class = RedHatStrategy
class CentOSHostname(Hostname):
    platform = 'Linux'
    distribution = 'Centos'
    strategy_class = RedHatStrategy
class ClearLinuxHostname(Hostname):