overit_network fails when trying to create a network that uses an external provider.

##### ISSUE TYPE
- Bug Report

##### COMPONENT NAME
module ovirt_network


##### ANSIBLE VERSION
```
ansible 2.9.1
  config file = /Users/krist/Work/INFRA/Bern/PlopslandRHEV/ansible.cfg
  configured module search path = ['/Users/krist/.ansible/plugins/modules', '/usr/share/ansible/plugins/modules']
  ansible python module location = /usr/local/Cellar/ansible/2.9.1/libexec/lib/python3.7/site-packages/ansible
  executable location = /usr/local/bin/ansible
  python version = 3.7.5 (default, Nov  1 2019, 02:16:23) [Clang 11.0.0 (clang-1100.0.33.8)]##### CONFIGURATION
```
##### OS / ENVIRONMENT

MacOSX 10.15

##### STEPS TO REPRODUCE
Consider the following playbook:

```
- name: prepare the RHEV cluster 
  hosts: localhost


  tasks:

  - block:
      - name: Obtain SSO Token
        ovirt_auth:
          url: "{{ ovirt_api }}"
          username: admin@internal
          ca_file: files/ca.pem
          password: "{{ ovirt_password }}"
    
      - name: Create private networks
        ovirt_network:
          auth: "{{ ovirt_auth }}"
          data_center: Default
          name: boot
          vm_network: true
          external_provider: ovirt-provider-ovn
          state: present

    always:
      - name: Always revoke the SSO token
        ovirt_auth:
          state: absent
          ovirt_auth: "{{ ovirt_auth }}"
```

##### EXPECTED RESULTS

A network "boot" is created, using the external provider ovirt-provider-ovn

##### ACTUAL RESULTS

An error is thrown: 

```
TASK [Create private networks] *********************************************************************************************************
An exception occurred during task execution. To see the full traceback, use -vvv. The error was: Exception: Entity 'boot' was not found.
fatal: [localhost]: FAILED! => {"changed": false, "msg": "Entity 'boot' was not found."}
```

Looking at hte source it appears then when you define a external provider that was is in fact attempted is to import a network form that external provider, not crearte one:

```
  if module.params.get('external_provider'):
                ret = networks_module.import_external_network()
            else:
                ret = networks_module.create(search_params=search_params)
```

That is not what you would expect, not according to the docs anyway.


else:
                ret = networks_module.create(search_params=search_params)
            
            if module.params.get('clusters') is not None:
                for param_cluster in module.params.get('clusters'):
                    cluster = search_by_name(clusters_service, param_cluster.get('name'))
                    if cluster is None:
                        raise Exception("Cluster '%s' was not found." % param_cluster.get('name'))
                    cluster_networks_service = clusters_service.service(cluster.id).networks_service()
                    cluster_networks_module = ClusterNetworksModule(
                        network_id=ret['id'],
                        cluster_network=param_cluster,
                        connection=connection,
                        module=module,
                        service=cluster_networks_service,
                    )
                    if param_cluster.get('assigned', True):
                        ret = cluster_networks_module.create()
                    else:
                        ret = cluster_networks_module.remove()
        elif state == 'absent':
            ret = networks_module.remove(search_params=search_params)
        module.exit_json(**ret)
    except Exception as e:
        module.fail_json(msg=str(e), exception=traceback.format_exc())
    finally:
        connection.close(logout=auth.get('token') is None)
if __name__ == "__main__":
    main()