##### 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

```

for line in self.client.push(repository, tag=tag, stream=True, decode=True):
                        self.log(line, pretty_print=True)
                        if line.get('errorDetail'):
                            raise Exception(line['errorDetail']['message'])
                        status = line.get('status')
                        if status == 'Pushing':
                            changed = True
                    self.results['changed'] = changed
                except Exception as exc:
                    if re.search('unauthorized', str(exc)):
                        if re.search('authentication required', str(exc)):
                            self.fail("Error pushing image %s/%s:%s - %s. Try logging into %s first." %
                                      (registry, repo_name, tag, str(exc), registry))
                        else:
                            self.fail("Error pushing image %s/%s:%s - %s. Does the repository exist?" %
                                      (registry, repo_name, tag, str(exc)))
                    self.fail("Error pushing image %s: %s" % (repository, str(exc)))
                self.results['image'] = self.client.find_image(name=repository, tag=tag)
                if not self.results['image']:
                    self.results['image'] = dict()
                self.results['image']['push_status'] = status
    def tag_image(self, name, tag, repository, push=False):
        '''
        Tag an image into a repository.
        :param name: name of the image. required.
        :param tag: image tag.
        :param repository: path to the repository. required.
        :param push: bool. push the image once it's tagged.
        :return: None
        '''