##### 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

```

repo, repo_tag = parse_repository_tag(repository)
        if not repo_tag:
            repo_tag = "latest"
            if tag:
                repo_tag = tag
        image = self.client.find_image(name=repo, tag=repo_tag)
        found = 'found' if image else 'not found'
        self.log("image %s was %s" % (repo, found))
        if not image or self.force_tag:
            self.log("tagging %s:%s to %s:%s" % (name, tag, repo, repo_tag))
            self.results['changed'] = True
            self.results['actions'].append("Tagged image %s:%s to %s:%s" % (name, tag, repo, repo_tag))
            if not self.check_mode:
                try:
                    
                    
                    image_name = name
                    if tag and not re.search(tag, name):
                        image_name = "%s:%s" % (name, tag)
                    tag_status = self.client.tag(image_name, repo, tag=repo_tag, force=True)
                    if not tag_status:
                        raise Exception("Tag operation failed.")
                except Exception as exc:
                    self.fail("Error: failed to tag image - %s" % str(exc))
                self.results['image'] = self.client.find_image(name=repo, tag=repo_tag)
                if image and image['Id'] == self.results['image']['Id']:
                    self.results['changed'] = False
                if push:
                    self.push_image(repo, repo_tag)
    def build_image(self):