<!--- Verify first that your feature was not already discussed on GitHub -->
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##### SUMMARY
<!--- Describe the new feature/improvement briefly below -->
Currently it's not possible to specify disks to be included in the snapshot, always all disks are used.

##### ISSUE TYPE
- Feature Idea

##### COMPONENT NAME
<!--- Write the short name of the module, plugin, task or feature below, use your best guess if unsure -->
ovirt_snapshot

##### ADDITIONAL INFORMATION
<!--- Describe how the feature would be used, why it is needed and what it would solve -->

<!--- Paste example playbooks or commands between quotes below -->
Could look like:
```yaml
ovirt_snapshot:
  description: My snap
  vm_name: myvm
  disks:
    - id: 123
    - id: 456
```

or 

```yaml
ovirt_snapshot:
  description: My snap
  vm_name: myvm
  disks:
    - name: myvm_disk_db
    - name: myvm_disk_store
```

<!--- HINT: You can also paste gist.github.com links for larger files -->

def _transfer(transfer_service, proxy_connection, proxy_url, transfer_ticket):
        BUF_SIZE = 128 * 1024
        transfer_headers = {
            'Authorization': transfer_ticket,
        }
        proxy_connection.request(
            'GET',
            proxy_url.path,
            headers=transfer_headers,
        )
        r = proxy_connection.getresponse()
        path = module.params["download_image_path"]
        image_size = int(r.getheader('Content-Length'))
        with open(path, "wb") as mydisk:
            pos = 0
            while pos < image_size:
                to_read = min(image_size - pos, BUF_SIZE)
                chunk = r.read(to_read)
                if not chunk: