##### 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"}
```
required: false
    version_added: "2.2"
    type: list
    elements: str
  suspend_processes:
    description:
      - A list of scaling processes to suspend.
      - 'Valid values include:'
      - C(Launch), C(Terminate), C(HealthCheck), C(ReplaceUnhealthy), C(AZRebalance), C(AlarmNotification), C(ScheduledActions), C(AddToLoadBalancer)
      - 'Full documentation of valid values can be found in the AWS documentation:'
      - 'U(https://docs.aws.amazon.com/autoscaling/ec2/userguide/as-suspend-resume-processes.html)'
    default: []
    version_added: "2.3"
    type: list
    elements: str
  metrics_collection:
    description:
      - Enable ASG metrics collection.
    type: bool
    default: false
    version_added: "2.6"
  metrics_granularity:
    description:
      - When I(metrics_collection=true) this will determine the granularity of metrics collected by CloudWatch.
    default: "1Minute"
    version_added: "2.6"
    type: str
  metrics_list:
    description:
      - List of autoscaling metrics to collect when I(metrics_collection=true).