##### 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"}
```
try:
            launch_configs = describe_launch_configurations(connection, launch_config_name)
        except (botocore.exceptions.ClientError, botocore.exceptions.BotoCoreError) as e:
            module.fail_json(msg="Failed to describe launch configurations",
                             exception=traceback.format_exc())
        if len(launch_configs['LaunchConfigurations']) == 0:
            module.fail_json(msg="No launch config found with name %s" % launch_config_name)
        launch_object = {"LaunchConfigurationName": launch_configs['LaunchConfigurations'][0]['LaunchConfigurationName']}
        return launch_object
    elif launch_template:
        lt = describe_launch_templates(ec2_connection, launch_template)['LaunchTemplates'][0]
        if launch_template['version'] is not None:
            launch_object = {"LaunchTemplate": {"LaunchTemplateId": lt['LaunchTemplateId'], "Version": launch_template['version']}}
        else:
            launch_object = {"LaunchTemplate": {"LaunchTemplateId": lt['LaunchTemplateId'], "Version": str(lt['LatestVersionNumber'])}}
        if mixed_instances_policy:
            instance_types = mixed_instances_policy.get('instance_types', [])
            policy = {
                'LaunchTemplate': {
                    'LaunchTemplateSpecification': launch_object['LaunchTemplate']
                }
            }
            if instance_types:
                policy['LaunchTemplate']['Overrides'] = []
                for instance_type in instance_types:
                    instance_type_dict = {'InstanceType': instance_type}
                    policy['LaunchTemplate']['Overrides'].append(instance_type_dict)
            launch_object['MixedInstancesPolicy'] = policy
        return launch_object
def elb_dreg(asg_connection, group_name, instance_id):