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##### SUMMARY
<!--- Explain the problem briefly below -->
The ansible_distribution_version fact is displayed as "8" on Debian 9, when Plesk 18 is installed, because the /etc/plesk-release file is parsed.
It seems the setup module (_distro.py?) is parsing all /etc/*-release files on a target host, and this can mess with the ansible_distribution_version facts.

##### ISSUE TYPE
- Bug Report

##### COMPONENT NAME
<!--- Write the short name of the module, plugin, task or feature below, use your best guess if unsure -->
setup

##### ANSIBLE VERSION
<!--- Paste verbatim output from "ansible --version" between quotes -->
```paste below
ansible 2.8.6
  config file = /etc/ansible/ansible.cfg
  configured module search path = ['/root/.ansible/plugins/modules', '/usr/share/ansible/plugins/modules']
  ansible python module location = /usr/local/lib/python3.5/dist-packages/ansible
  executable location = /usr/local/bin/ansible
  python version = 3.5.3 (default, Sep 27 2018, 17:25:39) [GCC 6.3.0 20170516]
```

##### OS / ENVIRONMENT
<!--- Provide all relevant information below, e.g. target OS versions, network device firmware, etc. -->
```
root@web003:~# cat /etc/os-release
PRETTY_NAME="Debian GNU/Linux 9 (stretch)"
NAME="Debian GNU/Linux"
VERSION_ID="9"
VERSION="9 (stretch)"
VERSION_CODENAME=stretch
ID=debian
HOME_URL="https://www.debian.org/"
SUPPORT_URL="https://www.debian.org/support"
BUG_REPORT_URL="https://bugs.debian.org/"

root@web003:~# lsb_release -a
No LSB modules are available.
Distributor ID: Debian
Description:    Debian GNU/Linux 9.11 (stretch)
Release:        9.11
Codename:       stretch
```

##### STEPS TO REPRODUCE
<!--- Describe exactly how to reproduce the problem, using a minimal test-case -->
Install Debian with Plesk 18, and run ansible setup against it.
If you can't install Plesk, just create the file /etc/plesk-release with this content:

```
18.0.19.3
Plesk Obsidian 18.0
```

<!--- Paste example playbooks or commands between quotes below -->
```yaml
ansible web003 -m setup -a "filter=ansible_dist*"
```

<!--- HINT: You can paste gist.github.com links for larger files -->

##### EXPECTED RESULTS
<!--- Describe what you expected to happen when running the steps above -->
`ansible_distribution_version` reports 9

```
    "ansible_facts": {
        "ansible_distribution": "Debian",
        "ansible_distribution_file_parsed": true,
        "ansible_distribution_file_path": "/etc/os-release",
        "ansible_distribution_file_variety": "Debian",
        "ansible_distribution_major_version": "9",
        "ansible_distribution_release": "stretch",
        "ansible_distribution_version": "9.11",
        "discovered_interpreter_python": "/usr/bin/python"
```

##### ACTUAL RESULTS
<!--- Describe what actually happened. If possible run with extra verbosity (-vvvv) -->
<!--- Paste verbatim command output between quotes -->
`ansible_distribution_version` reports 8

```paste below
    "ansible_facts": {
        "ansible_distribution": "Debian",
        "ansible_distribution_file_parsed": true,
        "ansible_distribution_file_path": "/etc/os-release",
        "ansible_distribution_file_variety": "Debian",
        "ansible_distribution_major_version": "8",
        "ansible_distribution_release": "stretch",
        "ansible_distribution_version": "8.0.19.3",
        "discovered_interpreter_python": "/usr/bin/python"
```

"""A version of @property which caches the value.  On access, it calls the
    underlying function and sets the value in `__dict__` so future accesses
    will not re-call the property.
    """
    def __init__(self, f):
        self._fname = f.__name__
        self._f = f
    def __get__(self, obj, owner):
        assert obj is not None, 'call {0} on an instance'.format(self._fname)
        ret = obj.__dict__[self._fname] = self._f(obj)
        return ret
class LinuxDistribution(object):
    """
    Provides information about a OS distribution.
    This package creates a private module-global instance of this class with
    default initialization arguments, that is used by the
    `consolidated accessor functions`_ and `single source accessor functions`_.
    By using default initialization arguments, that module-global instance
    returns data about the current OS distribution (i.e. the distro this
    package runs on).
    Normally, it is not necessary to create additional instances of this class.
    However, in situations where control is needed over the exact data sources
    that are used, instances of this class can be created with a specific
    distro release file, or a specific os-release file, or without invoking the
    lsb_release command.
    """
    def __init__(self,