aws: Graceful handling of EC2 detach errors
aws: Graceful handling of EC2 detach errors

Sometimes, we observe the following error during a rolling update:

error detaching instance "i-XXXX", node "ip-10-X-X-X.ec2.internal": error detaching instance "i-XXXX": ValidationError: The instance i-XXXX is not part of Auto Scaling group XXXXX

The sequence of events that lead to this problem is the following:

- A new ASG object is being built from the launch template
- Existing instances are being added to it
- An existing instance is being ignored because it's already terminating
W0205 08:01:32.593377     191 aws_cloud.go:791] ignoring instance as it is terminating: i-XXXX in autoscaling group: XXXX
- Due to maxSurge, the terminating instance is trying to be detached
  from the autoscaling group and fails.

As such, in case of EC@ ASG deatch failures we can simply try to detach
the next node instead of aborting the whole update operation.

kubernetes/kops,kubernetes/kops,justinsb/kops,justinsb/kops,kubernetes/kops,justinsb/kops