##### 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

```

params['cache_from'] = self.cache_from
        if self.network:
            params['network_mode'] = self.network
        if self.use_config_proxy:
            params['use_config_proxy'] = self.use_config_proxy
            
            
            if 'buildargs' not in params:
                params['buildargs'] = {}
        if self.target:
            params['target'] = self.target
        for line in self.client.build(**params):
            
            self.log(line, pretty_print=True)
            if "stream" in line:
                build_output.append(line["stream"])
            if line.get('error'):
                if line.get('errorDetail'):
                    errorDetail = line.get('errorDetail')
                    self.fail(
                        "Error building %s - code: %s, message: %s, logs: %s" % (
                            self.name,
                            errorDetail.get('code'),
                            errorDetail.get('message'),
                            build_output))
                else:
                    self.fail("Error building %s - message: %s, logs: %s" % (
                        self.name, line.get('error'), build_output))
        return self.client.find_image(name=self.name, tag=self.tag)
    def load_image(self):