[cloud] EC2_ASG Set desired capacity to min_size if no instances exist (#30987)

* Set desired capacity to min_size if no instances exist

* Improve readability of if/then clause

* Only update null desired_capacity to min_size on initial create

Any future updates to the ASG will be able to reference the existing
capacity.

lib/ansible/modules/cloud/amazon/ec2_asg.py

@@ -806,6 +806,8 @@ def create_autoscaling_group(connection, module):
         launch_configs = describe_launch_configurations(connection, launch_config_name)
         if len(launch_configs['LaunchConfigurations']) == 0:
             module.fail_json(msg="No launch config found with name %s" % launch_config_name)
+        if desired_capacity is None:
+            desired_capacity = min_size
         ag = dict(
             AutoScalingGroupName=group_name,
             LaunchConfigurationName=launch_configs['LaunchConfigurations'][0]['LaunchConfigurationName'],
@@ -952,9 +954,13 @@ def create_autoscaling_group(connection, module):
                     attach_lb_target_groups(connection, group_name, list(tgs_to_attach))
 
         # check for attributes that aren't required for updating an existing ASG
-        desired_capacity = desired_capacity if desired_capacity is not None else as_group['DesiredCapacity']
-        min_size = min_size if min_size is not None else as_group['MinSize']
-        max_size = max_size if max_size is not None else as_group['MaxSize']
+        # check if min_size/max_size/desired capacity have been specified and if not use ASG values
+        if min_size is None:
+            min_size = as_group['MinSize']
+        if max_size is None:
+            max_size = as_group['MaxSize']
+        if desired_capacity is None:
+            desired_capacity = as_group['DesiredCapacity']
         launch_config_name = launch_config_name or as_group['LaunchConfigurationName']
 
         launch_configs = describe_launch_configurations(connection, launch_config_name)