##### SUMMARY
docker_image module is missing etc_hosts parameter even if this is documented and accepted by docker.build() as  of https://docker-py.readthedocs.io/en/stable/images.html

The same argument is accepted by docker_run but the lack of support here prevents us from building images when extra_hosts is needed.

I mention that the only reason why I propose using `etc_hosts` is in order to keep it in sync with already existing implementation from `docker_container` module which accepts `etc_hosts` which is translated to `extra_hosts` on docker-python-api.

I would personally prefer to use the same names as docker-api but this would require changing docker_container too.

##### ISSUE TYPE
- Bug Report

##### COMPONENT NAME
docker_image

##### ANSIBLE VERSION
<!--- Paste verbatim output from "ansible --version" between quotes -->
```paste below
ansible-devel
```

##### CONFIGURATION
<!--- Paste verbatim output from "ansible-config dump --only-changed" between quotes -->
```paste below

```

##### OS / ENVIRONMENT
<!--- Provide all relevant information below, e.g. target OS versions, network device firmware, etc. -->


##### STEPS TO REPRODUCE
<!--- Describe exactly how to reproduce the problem, using a minimal test-case -->

<!--- Paste example playbooks or commands between quotes below -->
```yaml

```

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

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


##### ACTUAL RESULTS
<!--- Describe what actually happened. If possible run with extra verbosity (-vvvv) -->

<!--- Paste verbatim command output between quotes -->
```paste below

```

'''
        Archive an image to a .tar file. Called when archive_path is passed.
        :param name - name of the image. Type: str
        :return None
        '''
        if not tag:
            tag = "latest"
        image = self.client.find_image(name=name, tag=tag)
        if not image:
            self.log("archive image: image %s:%s not found" % (name, tag))
            return
        image_name = "%s:%s" % (name, tag)
        self.results['actions'].append('Archived image %s to %s' % (image_name, self.archive_path))
        self.results['changed'] = True
        if not self.check_mode:
            self.log("Getting archive of image %s" % image_name)
            try:
                image = self.client.get_image(image_name)
            except Exception as exc:
                self.fail("Error getting image %s - %s" % (image_name, str(exc)))
            try:
                with open(self.archive_path, 'wb') as fd: