##### 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"}
```
properties['unhealthy_instances'] += 1
            if i['LifecycleState'] == 'InService':
                properties['in_service_instances'] += 1
            if i['LifecycleState'] == 'Terminating':
                properties['terminating_instances'] += 1
            if i['LifecycleState'] == 'Pending':
                properties['pending_instances'] += 1
    else:
        properties['instances'] = []
    properties['auto_scaling_group_name'] = autoscaling_group.get('AutoScalingGroupName')
    properties['auto_scaling_group_arn'] = autoscaling_group.get('AutoScalingGroupARN')
    properties['availability_zones'] = autoscaling_group.get('AvailabilityZones')
    properties['created_time'] = autoscaling_group.get('CreatedTime')
    properties['instance_facts'] = instance_facts
    properties['load_balancers'] = autoscaling_group.get('LoadBalancerNames')
    if autoscaling_group.get('LaunchConfigurationName'):
        properties['launch_config_name'] = autoscaling_group.get('LaunchConfigurationName')
    else:
        properties['launch_template'] = autoscaling_group.get('LaunchTemplate')
    properties['tags'] = autoscaling_group.get('Tags')
    properties['min_size'] = autoscaling_group.get('MinSize')
    properties['max_size'] = autoscaling_group.get('MaxSize')
    properties['desired_capacity'] = autoscaling_group.get('DesiredCapacity')
    properties['default_cooldown'] = autoscaling_group.get('DefaultCooldown')
    properties['healthcheck_grace_period'] = autoscaling_group.get('HealthCheckGracePeriod')
    properties['healthcheck_type'] = autoscaling_group.get('HealthCheckType')
    properties['default_cooldown'] = autoscaling_group.get('DefaultCooldown')
    properties['termination_policies'] = autoscaling_group.get('TerminationPolicies')
    properties['target_group_arns'] = autoscaling_group.get('TargetGroupARNs')
    properties['vpc_zone_identifier'] = autoscaling_group.get('VPCZoneIdentifier')