Rolling termination working.  Fixes #8501.

This adds the the ability to, in a rolling fashion, replace instances in an ASG that are assigned an old launch configuration, with instances that are assigned a current launch configuration.

This would allow you to, for an example, take a new AMI, create a new launch config with it, and assign that new launch config to the ASG. Then in a rolling fashion, the module will terminate all instances that had the old launch configuration and replace them with new ones.  It will wait for instances to be in a healthy state as determined by ec2_asg health_check_type parameter (EC2/ELB) before continuing.

For folks who are pre-baking their AMIs and using ASGs, this should solve the problem of rolling updates.   The pull request has 2 different approaches that are supported, those are outlined in the module docs and examples.