adding option to add extra nodes to each asg

[crosbymichael1]

When cluster-autoscaler is disabled during the upgrade process this causes new pods being scheduled onto the cluster to be stuck in Pending until the script finishes running and cluster autoscaler is turned back on. Adding additional nodes to the cluster prior to the upgrade can help circumvent this issue and then when cluster auto-scaler is turned back on it can remove unneeded nodes. This is especially needed in Production Cluster where upgrades can take hours and we still want to account for being able to schedule new Pods on the cluster.

[crosbymichael1]

@crhuber Could I get some eyes on this please. Its something I need as a use case where I work.

[crosbymichael1]

@chadlwilson are you able to review this please?

[chadlwilson]

I'm not a maintainer here so can't review things. I'm also not actively using eks-rolling-update any longer so not well set up to give useful input and think about how all the options interact with one another.