##### SUMMARY

When using the `ec2_asg` module with `replace_all_instances: yes`, then `wait_for_instances` is effectively ignored. 

I would expect that if `wait_for_instances: no` then it would not wait for instances to complete starting/termination. 


##### ISSUE TYPE
- Bug Report

##### COMPONENT NAME
ec2_asg 

##### ANSIBLE VERSION
<!--- Paste verbatim output from "ansible --version" between quotes -->
```
ansible 2.9.2
  config file = None
  configured module search path = ['/home/user/.ansible/plugins/modules', '/usr/share/ansible/plugins/modules']
  ansible python module location = /home/user/.local/lib/python3.7/site-packages/ansible
  executable location = /home/user/.local/bin/ansible
  python version = 3.7.5 (default, Nov 20 2019, 09:21:52) [GCC 9.2.1 20191008]
```

##### CONFIGURATION
<!--- Paste verbatim output from "ansible-config dump --only-changed" between quotes -->
``` 
(empty) 
```

##### OS / ENVIRONMENT
OS: Ubuntu 19.10
Ansible installed via pip3 

##### STEPS TO REPRODUCE
```
- name: Update ASG
  ec2_asg:
    name: "my-asg" 
    launch_config_name: "my-launchconfig"
    min_size: 1       
    max_size:  1
    replace_batch_size: 1
    replace_all_instances: yes
    wait_for_instances: no
```

This will not return successfully until new instance(s) have started, and any existing instance(s) have completed termination. 

If your timeout is not set long enough, then you'll get a 'Waited too long for old instances to terminate' response.  

##### EXPECTED RESULTS

I would expect that it would issue commands to terminate old instances and start new instances, without waiting. 

For those who have to replace in smaller batches than the current `desired_capacity`, then they would need to set `wait_for_instances: yes`.  Perhaps a warning might be in order if `replace_batch_size` is less than `desired_capacity`

##### ACTUAL RESULTS

Playbook output when it takes too long to execute: 

```
TASK [test : Update ASG] ***********************************************************************************************************************************************
fatal: [localhost]: FAILED! => {"changed": false, "msg": "Waited too long for old instances to terminate. Wed Dec 18 12:51:55 2019"}
```
if not HAS_BOTO3:
        module.fail_json(msg='boto3 required for this module')
    if module.params.get('mixed_instance_type') and not module.botocore_at_least('1.12.45'):
        module.fail_json(msg="mixed_instance_type is only supported with botocore >= 1.12.45")
    state = module.params.get('state')
    replace_instances = module.params.get('replace_instances')
    replace_all_instances = module.params.get('replace_all_instances')
    region, ec2_url, aws_connect_params = get_aws_connection_info(module, boto3=True)
    connection = boto3_conn(module,
                            conn_type='client',
                            resource='autoscaling',
                            region=region,
                            endpoint=ec2_url,
                            **aws_connect_params)
    changed = create_changed = replace_changed = False
    exists = asg_exists(connection)
    if state == 'present':
        create_changed, asg_properties = create_autoscaling_group(connection)
    elif state == 'absent':
        changed = delete_autoscaling_group(connection)
        module.exit_json(changed=changed)
    
    if exists and (replace_all_instances or replace_instances) and (module.params.get('launch_config_name') or module.params.get('launch_template')):
        replace_changed, asg_properties = replace(connection)
    if create_changed or replace_changed:
        changed = True
    module.exit_json(changed=changed, **asg_properties)
if __name__ == '__main__':
    main()