##### 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"}
```
asg_properties = get_properties(as_group)
            changed = True
            return changed, asg_properties
        except botocore.exceptions.ClientError as e:
            module.fail_json(msg="Failed to create Autoscaling Group.",
                             exception=traceback.format_exc(), **camel_dict_to_snake_dict(e.response))
        except botocore.exceptions.BotoCoreError as e:
            module.fail_json(msg="Failed to create Autoscaling Group.",
                             exception=traceback.format_exc())
    else:
        as_group = as_groups[0]
        initial_asg_properties = get_properties(as_group)
        changed = False
        if suspend_processes(connection, as_group):
            changed = True
        
        if len(set_tags) > 0:
            have_tags = as_group.get('Tags')
            want_tags = asg_tags
            if have_tags:
                have_tags.sort(key=lambda x: x["Key"])
            if want_tags:
                want_tags.sort(key=lambda x: x["Key"])
            dead_tags = []
            have_tag_keyvals = [x['Key'] for x in have_tags]
            want_tag_keyvals = [x['Key'] for x in want_tags]
            for dead_tag in set(have_tag_keyvals).difference(want_tag_keyvals):
                changed = True
                dead_tags.append(dict(ResourceId=as_group['AutoScalingGroupName'],
                                      ResourceType='auto-scaling-group', Key=dead_tag))