##### 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

```

# Image will be centos:7
    name: centos
    # Will be pushed to localhost:5000/centos:7
    repository: localhost:5000/centos
    tag: 7
    push: yes
    source: local
- name: Add tag latest to image
  docker_image:
    name: myimage:7.1.2
    repository: myimage:latest
    source: local
- name: Remove image
  docker_image:
    state: absent
    name: registry.ansible.com/chouseknecht/sinatra
    tag: v1
- name: Build an image and push it to a private repo
  docker_image:
    build:
      path: ./sinatra
    name: registry.ansible.com/chouseknecht/sinatra
    tag: v1
    push: yes
    source: build
- name: Archive image
  docker_image:
    name: registry.ansible.com/chouseknecht/sinatra
    tag: v1
    archive_path: my_sinatra.tar