Add support for multiple ASGs in rolling deployment command

[mikeandersen]

Currently, kubergrunt requires a single --asg-name when running eks deploy but in many clusters you'll have multiple ASGs for your worker nodes.

It would be great if this supported providing a list of ASGs and running rolling deployments on each of them.

[friedrich-brunzema]

Yes, I ran into this issue too -- problem is running one asg-name does not work in a multi-load balancer scenario because kubergrunt tries to get all the load balancers. Another issue is if you have a cluster autoscaler, it will kill any extra nodes that kubergrunt creates to bring the system back to nominal.

INFO[2020-04-01T12:37:39-04:00] Detected cluster deployed in region us-east-2  name=kubergrunt
INFO[2020-04-01T12:37:40-04:00] Successfully retrieved EKS cluster details    name=kubergrunt
INFO[2020-04-01T12:37:40-04:00] Found 15 LoadBalancer services of 162 services in kubernetes.  name=kubergrunt
INFO[2020-04-01T12:37:40-04:00] Successfully extracted loadbalancer names     name=kubergrunt
INFO[2020-04-01T12:37:40-04:00] Verifying new nodes are registered to external load balancers.  name=kubergrunt```