##### 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

```

- Timeout for HTTP requests during the image build operation. Provide a positive integer value for the number of
        seconds.
      - Please use I(build.http_timeout) instead. This option will be removed in Ansible 2.12.
    type: int
    version_added: "2.1"
  name:
    description:
      - "Image name. Name format will be one of: name, repository/name, registry_server:port/name.
        When pushing or pulling an image the name can optionally include the tag by appending ':tag_name'."
      - Note that image IDs (hashes) are not supported.
    type: str
    required: yes
  path:
    description:
      - Use with state 'present' to build an image. Will be the path to a directory containing the context and
        Dockerfile for building an image.
      - Set I(source) to C(build) if you want to build the image. The option will
        be set automatically before Ansible 2.12 if this option is used. From Ansible 2.12
        on, you have to set I(source) to C(build).
      - Please use I(build.path) instead. This option will be removed in Ansible 2.12.
    type: path
    aliases:
      - build_path
  pull:
    description:
      - When building an image downloads any updates to the FROM image in Dockerfile.
      - Please use I(build.pull) instead. This option will be removed in Ansible 2.12.
      - The default is currently C(yes). This will change to C(no) in Ansible 2.12.
    type: bool
    version_added: "2.1"