##### 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

```

description:
      - Use with state I(absent) to un-tag and remove all images matching the specified name. Use with state
        C(present) to build, load or pull an image when the image already exists. Also use with state C(present)
        to force tagging an image.
      - Please stop using this option, and use the more specialized force options
        I(force_source), I(force_absent) and I(force_tag) instead.
      - This option will be removed in Ansible 2.12.
    type: bool
    version_added: "2.1"
  force_source:
    description:
      - Use with state C(present) to build, load or pull an image (depending on the
        value of the I(source) option) when the image already exists.
    type: bool
    default: false
    version_added: "2.8"
  force_absent:
    description:
      - Use with state I(absent) to un-tag and remove all images matching the specified name.
    type: bool
    default: false
    version_added: "2.8"
  force_tag:
    description:
      - Use with state C(present) to force tagging an image.
    type: bool
    default: false
    version_added: "2.8"
  http_timeout:
    description: