##### 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

```

push:
    description:
      - Push the image to the registry. Specify the registry as part of the I(name) or I(repository) parameter.
    type: bool
    default: no
    version_added: "2.2"
  rm:
    description:
      - Remove intermediate containers after build.
      - Please use I(build.rm) instead. This option will be removed in Ansible 2.12.
    type: bool
    default: yes
    version_added: "2.1"
  nocache:
    description:
      - Do not use cache when building an image.
      - Please use I(build.nocache) instead. This option will be removed in Ansible 2.12.
    type: bool
    default: no
  repository:
    description:
      - Full path to a repository. Use with state C(present) to tag the image into the repository. Expects
        format I(repository:tag). If no tag is provided, will use the value of the C(tag) parameter or I(latest).
    type: str
    version_added: "2.1"
  state:
    description:
      - Make assertions about the state of an image.
      - When C(absent) an image will be removed. Use the force option to un-tag and remove all images
        matching the provided name.